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diff --git a/docs/source/lang/cpp/arithmetic.rst b/docs/source/lang/cpp/arithmetic.rst new file mode 100644 index 0000000..cef3954 --- /dev/null +++ b/docs/source/lang/cpp/arithmetic.rst @@ -0,0 +1,124 @@ +.. highlight:: cpp + +.. _lang-arithmetic: + +Arithmetic Operators (``+``, ``-``, ``*``, ``/``) +================================================= + +The operators ``+``, ``-``, ``*``, and ``/`` respectively evaluate to +the sum, difference, product, or quotient (respectively) of the two +operands. The operation is conducted using the data type of the +operands, so, for example, ``9 / 4`` gives ``2`` since 9 and 4 are +:ref:`int variables <lang-int>`. + +This also means that the operation can overflow if the result is +larger than that which can be stored in the data type (e.g. adding 1 +to an :ref:`lang-int` with the value 2,147,483,647 gives +-2,147,483,648). + +.. _lang-arithmetic-typeconversion: + +If the operands are of different types, the "larger" type is used for +the calculation. If one of the numbers (operands) are of the type +**float** or of type **double**, floating point math will be used for +the calculation. + +.. note:: The specifics of these rules are beyond the scope of this + documentation; for more information, see `The C++ Programming + Language <http://www2.research.att.com/~bs/3rd.html>`_\ , by Bjarne + Stroustroup, Appendix C, especially §§C.4-C.6, or `this WikiBooks + entry on C++ type conversion + <http://en.wikibooks.org/wiki/C%2B%2B_Programming/Programming_Languages/C%2B%2B/Code/Statements/Variables/Type_Casting#Automatic_type_conversion>`_. + +.. note:: For more information on how computers represent integers, + see the Wikipedia page on `two's complement + <http://en.wikipedia.org/wiki/Two's_complement>`_. + +.. contents:: Contents + :local: + +Examples +-------- + + :: + + y = y + 3; + x = x - 7; + i = j * 6; + r = r / 5; + + +Syntax +------ + + :: + + result = value1 + value2; + result = value1 - value2; + result = value1 * value2; + result = value1 / value2; + + +Parameters +---------- + +**value1**: any numeric variable or constant + +**value2**: any numeric variable or constant + +Programming Tips +---------------- + +- Know that :ref:`integer constants <lang-constants-integers>` + default to :ref:`int <lang-int>`, so some constant calculations + may overflow (e.g., 200000 * 5000000 will yield a negative result). + +- Choose variable sizes that are large enough to hold the largest + results from your calculations. + +- Know at what point your variable will "roll over" and also what + happens in the other direction e.g. (0 - 1) for unsigned arithmetic, + or (0 - -2,147,483,648) for signed arithmetic. + +- For math that requires fractions, float variables may be used, but + be aware of their drawbacks: large size and slow computation speeds + (the STM32 has no floating point hardware, so all floating point + calculations have to be done in software). + +- Use cast operator, e.g. ``(int)myFloat`` to convert one variable type + to another on the fly. + +Arduino Compatibility +--------------------- + +Since the STM32 processor on the Maple is a 32-bit machine, the int +type overflows at a much higher value on Maple than on Arduino. In +particular, on Maple, ints do not overflow (become negative) until +they reach 2,147,483,648; on the Arduino, they overflow at 32,767. +Because of this, programs running on Maple are much less likely to run +into overflow issues. The following table summarizes the sizes and +ranges of integer datatypes on the Maple (the ranges of ``long long`` +types are approximate): + +.. _lang-arithmetic-int-sizes: + +.. csv-table:: + :header: Datatype, Unsigned range, Signed range, Size (bytes) + :widths: 8, 12, 17, 8 + + ``char``, 0 --- 255, -128 --- 127, 1 + ``short``, "0 --- 65,535", "-32,768 --- 32,767", 2 + ``int``, "0 --- 4,294,967,295", "-2,147,483,648 --- 2,147,483,647", 4 + ``long``, "0 --- 4,294,967,295", "-2,147,483,648 --- 2,147,483,647", 4 + ``long long``, "0 --- 1.8*10\ :sup:`19`\ " (approx.), "-9.2*10\ :sup:`18` --- 9.2*10\ :sup:`18` (approx.)", 8 + + +See Also +-------- + +- The individual sizes (in bits) of various available types are + defined in :ref:`libmaple_types.h <libmaple-libmaple_types>`. + +- :ref:`sizeof <lang-sizeof>`\ () + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/array.rst b/docs/source/lang/cpp/array.rst new file mode 100644 index 0000000..39d4d91 --- /dev/null +++ b/docs/source/lang/cpp/array.rst @@ -0,0 +1,121 @@ +.. highlight:: cpp + +.. _lang-array: + +Arrays +====== + +An array is a collection of variables that are accessed with an index +number. Arrays in the C++ programming language, in which the Maple is +programmed, can be complicated, but using simple arrays is relatively +straightforward. + +.. contents:: Contents + :local: + +Creating (Declaring) an Array +----------------------------- + +All of the methods below are valid ways to create (declare) an +array. :: + + int myInts[6]; + int myPins[] = {2, 4, 8, 3, 6}; + int mySensVals[6] = {2, 4, -8, 3, 2}; + char message[6] = "hello"; + +You can declare an array without initializing it, as with myInts. In +the line referring to myPins, we declare an array without explicitly +choosing a size. The compiler counts the elements and creates an +array of the appropriate size. + +Finally, you can both initialize and size your array, as in +mySensVals. Note that when declaring an array with elements of type +char, one more element than your initialization is required, to hold +the required `null character <http://en.wikipedia.org/wiki/Null-terminated_string>`_. + + +Accessing an Array +------------------ + + +.. compound:: + + Arrays are **zero indexed**; that is, referring to the array + initialization above, the first element of the array is at index 0, + hence :: + + mySensVals[0] == 2; + mySensVals[1] == 4 + + and so forth. + +It also means that in an array with ten elements, index nine is the +last element. Hence:: + + int myArray[10]={9,3,2,4,3,2,7,8,9,11}; + // myArray[9] contains 11 + // myArray[10] is invalid and contains random information (other memory address) + +For this reason, you should be careful in accessing arrays. Accessing +past the end of an array (using an index number greater than your +declared array size - 1) is reading from memory that is in use for +other purposes. Reading from these locations is probably not going to +do much except yield invalid data. Writing to random memory locations +is definitely a bad idea, and can often lead to unhappy results such +as crashes or program malfunction. This can also be a difficult bug to +track down. + +Unlike Basic or Java, the C compiler does no checking to see if array +access is within legal bounds of the array size that you have +declared. + + +To assign a value to an array +----------------------------- + :: + + mySensVals[0] = 10; + + +To retrieve a value from an array +--------------------------------- + + :: + + x = mySensVals[4]; + + +Arrays and ``for`` Loops +------------------------ + +Arrays are often manipulated inside :ref:`for loops <lang-for>`, where +the loop counter is used as the index for each array element. For +example, to print the elements of an array over the serial port, you +could do something like this:: + + int i; + for (i = 0; i < 5; i = i + 1) { + SerialUSB.println(myPins[i]); + } + + +Example +------- + +For a complete program that demonstrates the use of arrays, see the +Arduino `Knight Rider example +<http://www.arduino.cc/en/Tutorial/KnightRider>`_\ (which will run +unmodified on the Maple). + +Arduino Compatibility +--------------------- + +Arrays on Maple are identical those on Arduino. + +See Also +-------- + +- :ref:`Storing arrays in FLASH memory <arm-gcc-attribute-flash>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/assignment.rst b/docs/source/lang/cpp/assignment.rst new file mode 100644 index 0000000..6379298 --- /dev/null +++ b/docs/source/lang/cpp/assignment.rst @@ -0,0 +1,60 @@ +.. highlight:: cpp + +.. _lang-assignment: + +Assignment Operator (``=``) +=========================== + +Stores the value to the right of the equal sign in the variable to +the left of the equal sign. + +The single equal sign in the C++ programming language is called the +assignment operator. It has a different meaning than in algebra +class, where it indicated an equation or equality. The assignment +operator tells the microcontroller to evaluate whatever value or +expression is on the right side of the equal sign, and store it in +the variable to the left of the equal sign [#fgross]_. + +Example +------- + +:: + + int sensVal; // declare an integer variable named sensVal + sensVal = analogRead(0); // store the (digitized) input voltage at analog pin 0 in sensVal + +Programming Tips +---------------- + +The variable on the left side of the assignment operator (``=`` sign) +needs to be able to hold the value stored in it. If it is not large +enough to hold a value, the value stored in the variable will be +incorrect. + +Don't confuse the assignment operator ``=`` (single equal sign) with +the comparison operator ``==`` (double equal signs), which evaluates +whether two expressions are equal. + +Arduino Compatibility +--------------------- + +Assignments on the Maple are identical to those on Arduino. + +See Also +-------- + +- :ref:`if <lang-if>` +- :ref:`char <lang-char>` +- :ref:`int <lang-int>` +- :ref:`long long <lang-longlong>` + +.. rubric:: Footnotes + +.. [#fgross] Experienced C++ programmers know this to be an + oversimplification of what happens when the variable on the left + hand side is an object. See Richard Gillam's wonderful and scary + `The Anatomy of the Assignment Operator + <http://icu-project.org/docs/papers/cpp_report/the_anatomy_of_the_assignment_operator.html>`_ + for more information. + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/bitshift.rst b/docs/source/lang/cpp/bitshift.rst new file mode 100644 index 0000000..47413f2 --- /dev/null +++ b/docs/source/lang/cpp/bitshift.rst @@ -0,0 +1,143 @@ +.. highlight:: cpp + +.. _lang-bitshift: + +Bit Shift Operators (``<<``, ``>>``) +==================================== + +(Adapted from `The Bit Math Tutorial +<http://www.arduino.cc/playground/Code/BitMath>`_ in `The Arduino +Playground <http://www.arduino.cc/playground/Main/HomePage>`_\ ) + +There are two bit shift operators in C++: the left shift operator +``<<`` and the right shift operator ``>>``. These operators cause the +bits in the left operand to be shifted left or right by the number of +positions specified by the right operand. + +More information on bitwise math can be obtained in the Wikipedia +article on `bitwise operations +<http://en.wikipedia.org/wiki/Bitwise_operation>`_\ , especially the +section on shifts in `C, C++, and Java +<http://en.wikipedia.org/wiki/Bitwise_operation#Shifts_in_C.2C_C.2B.2B.2C_C.23_and_Java>`_\ . + + +Syntax +------ + +``some_int << number_of_bits`` + +``some_int >> number_of_bits`` + + +Parameters +---------- + +* **some_int** An integer value or variable. + +* **number_of_bits** integer whose value is at most ``8 * + sizeof(variable)`` (so ``number_of_bits`` can be at most 32 for + ``int`` values, at most ``8`` for ``char`` values, etc.; the various + integer sizes are summarized :ref:`in this table + <lang-arithmetic-int-sizes>`\ ). + + + +Example: +-------- + +Here are some examples of bit shifting, with the binary representation of the number in comments:: + + int a = 5; // binary: 101 + int b = a << 3; // binary: 101000, or 40 in decimal + int c = b >> 3; // binary: 101, or back to 5 like we started with + + +When you left shift a value x by y bits (x << y), the leftmost y bits +in x are lost, literally shifted out of existence. We'll do this +example with ``char`` values (which are integers in the range 0-255, +and take up 8 bits of memory):: + + char a = 5; // binary (all 8 bits): 00000101 + char b = a << 7; // binary: 10000000 - the first 1 in 101 was discarded + + +If you are certain that none of the ones in a value are being shifted +into oblivion, a simple way to think of the left-shift operator is +that it multiplies the left operand by 2 raised to the right operand +power (in math notation, ``x << y`` equals x * 2\ :sup:`y`\ , as long +as none of the bits of x get shifted out). For example, to generate +powers of 2, the following expressions can be employed:: + + 1 << 0 == 1 + 1 << 1 == 2 + 1 << 2 == 4 + 1 << 3 == 8 + ... + 1 << 8 == 256 + 1 << 9 == 512 + 1 << 10 == 1024 + ... + +.. _lang-bitshift-signbit-gotcha: + +When you shift x right by y bits (``x >> y``), and the highest bit in +x is a 1, the behavior depends on the exact data type of x. If x is of +type ``int``, the highest bit is special, and determines whether x is +negative or not; the details are too complicated to explain here, but +they are thoroughly explained in the Wikipedia article on `two's +complement arithmetic +<http://en.wikipedia.org/wiki/Two%27s_complement>`_\ , which the +system most computers use to store integers. In that case, the sign +bit is copied into lower bits, for esoteric historical reasons:: + + int x = -16; // binary (all 32 bits): 11111111111111111111111111110000 + int y = x >> 3; // binary: 11111111111111111111111111111110 + + + +This behavior, called "sign extension", is often not what you +want. You probably wish zeros to be shifted in from the left. It +turns out that the right shift rules are different for ``unsigned +int`` values, so you can use a type cast to suppress ones being copied +from the left:: + + int x = -16; // binary: 11111111111111111111111111110000 + int y = (unsigned int)x >> 3; // binary: 00011111111111111111111111111110 + + + +If you are careful to avoid sign extension, you can use the +right-shift operator, ``>>``, as a way to divide by powers of 2. For +example:: + + int x = 1000; + int y = x >> 3; // integer division of 1000 by 8, causing y = 125. + + +Arduino Compatibility +--------------------- + +Since it's part of the C++ language, bit shifting on the Maple is +compatible with the Arduino; however, you should keep in mind that the +Maple has bigger integer types (as in, more bits) than the Arduino. + +Since the STM32 is a 32-bit processor, the ``int`` type takes up 32 +bits instead of 16, like on Arduino's 16-bit microcontroller. This +means that you can shift left, like ``x << y``, with bigger values of +``y`` on the Maple before ones in ``x`` start to get shifted out. + +To calculate the number of bits of an integer type on the Maple, +multiply its size in bytes (see :ref:`this table +<lang-arithmetic-int-sizes>` for these) by 8, since there are 8 +bits in 1 byte. For example, a ``short`` takes up 2 bytes of memory, +or 2 * 8 = 16 bits. + +See Also +-------- + +- :ref:`lang-bit` +- :ref:`lang-bitread` +- :ref:`lang-bitwrite` +- :ref:`lang-bitclear` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/bitwisemath.rst b/docs/source/lang/cpp/bitwisemath.rst new file mode 100644 index 0000000..cfe34f2 --- /dev/null +++ b/docs/source/lang/cpp/bitwisemath.rst @@ -0,0 +1,185 @@ +.. highlight:: cpp + +.. _lang-bitwisemath: + +Bitwise Operators (``&``, ``|``, ``^``, ``~``) +============================================== + +The bitwise operators perform their calculations at the bit level of +variables. They help solve a wide range of common programming +problems. + +Much of the material here is adapted for Maple from an (Arduino) +`tutorial on bitwise math +<http://www.arduino.cc/playground/Code/BitMath>`_\ . Another great +resource is the Wikipedia article on `bitwise operations +<http://en.wikipedia.org/wiki/Bitwise_operation>`_\ . + +Below are descriptions and syntax for all of the operators. + +.. contents:: Contents + :local: + +.. _lang-bitwisemath-and: + +Bitwise AND (``&``) +------------------- + +The bitwise AND operator in C++ is a single ampersand, ``&``, used +between two other integer expressions. Bitwise AND operates on each +bit position of the surrounding expressions independently, according +to this rule: if both input bits are 1, the resulting output is 1, +otherwise the output is 0. Another way of expressing this is:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 0 0 1 (operand1 & operand2) = result + + +On the Maple, the type ``int`` is a 32-bit value, so using ``&`` +between two ``int`` expressions causes 32 simultaneous AND operations +to occur. In a code fragment like:: + + int a = 92; // in binary: 00000000000000000000000001011100 + int b = 101; // in binary: 00000000000000000000000001100101 + int c = a & b; // result: 00000000000000000000000001000100, + // (or 68 in decimal). + + +Each of the 32 bits in ``a`` and ``b`` are processed using bitwise +AND, and all 32 resulting bits are stored in ``c``, resulting in the +value 1000100 in binary, which is 68 in decimal. + + +.. _lang-bitwisemath-or: + +Bitwise OR (``|``) +------------------ + +The bitwise OR operator in C++ is the vertical bar symbol, ``|``. Like +the ``&`` operator, ``|`` operates independently on each bit in its +two surrounding integer expressions, but what it does is +different. The bitwise OR of two bits is 1 if either or both of the +input bits is 1, otherwise it is 0. For example:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 1 1 1 (operand1 | operand2) = result + +Here is an example of bitwise OR used in a snippet of C++ code (using +``char``, which takes up 8 bits of memory, instead of ``int``, which +uses 32):: + + char a = 92; // in binary: 01011100 + char b = 101; // in binary: 01100101 + char c = a | b; // result: 01111101, or 125 in decimal. + +.. _lang-bitwisemath-xor: + +Bitwise XOR (``^``) +------------------- + +There is a somewhat unusual operator in C++ called bitwise EXCLUSIVE +OR, also known as bitwise XOR. (In English, this is usually pronounced +"zor" or "ex-or"). The bitwise XOR operator is written using the caret +symbol, ``^``. This operator is very similar to the bitwise OR +operator ``|``, except it evaluates to 0 for a given bit position when +both of the input bits for that position are 1:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 1 1 0 (operand1 ^ operand2) = result + + +Another way to look at bitwise XOR is that each bit in the result +is a 1 if the input bits are different, or 0 if they are the same. + +Here is a simple example:: + + int x = 12; // binary (ignoring extra bits): 1100 + int y = 10; // binary: 1010 + int z = x ^ y; // binary: 0110, or decimal 6 + + + +The ^ operator is often used to toggle (i.e. change from 0 to 1, or 1 +to 0) some of the bits in an integer expression. In a bitwise OR +operation if there is a 1 in the mask bit, that bit is inverted; if +there is a 0, the bit is not inverted and stays the same. Below is a +program to toggle the built-in LED pin (you can also accomplish this +with :ref:`lang-toggleled`):: + + // Toggle built-in LED pin + + int toggle = 0; + + // demo for Exclusive OR + void setup(){ + pinMode(BOARD_LED_PIN, OUTPUT); + } + + void loop(){ + toggle = toggle ^ 1; + digitalWrite(BOARD_LED_PIN, toggle); + delay(100); + } + +.. _lang-bitwisemath-not: + +Bitwise NOT (``~``) +------------------- + +The bitwise NOT operator in C++ is the tilde character ``~``. Unlike +``&`` and ``|``, the bitwise NOT operator is applied to a single +operand to its right. Bitwise NOT changes each bit to its opposite: 0 +becomes 1, and 1 becomes 0. For example:: + + 0 1 operand1 + ---- + 1 0 ~operand1 = result + +Another example:: + + char a = 103; // binary: 01100111 + char b = ~a; // binary: 10011000 = -104 + +You might be surprised to see a negative number like -104 as the +result of this operation. This is because the highest bit in an int +variable is the so-called "sign bit". If the highest bit is 1, the +number is interpreted as negative. This encoding of positive and +negative numbers is referred to as *two's complement*. For more +information, see the Wikipedia article on `two's +complement. <http://en.wikipedia.org/wiki/Twos_complement>`_ + +As an aside, it is interesting to note that (under two's complement +arithmetic) for any integer ``x``, ``~x`` is the same as ``-x-1``. + +At times, the sign bit in a signed integer expression can cause +some unwanted surprises. + + +Uses +---- + +One of the most common uses of bitwise operations is to select or +manipulate a particular bit (or bits) from an integer value, often +called `bit masking +<http://en.wikipedia.org/wiki/Mask_%28computing%29>`_\ . See the +linked Wikipedia article for more information and examples. + +If you really want to see bit-twiddling techniques in their full +glory, you could do much worse than to get yourself a copy of +`Hacker's Delight <http://www.hackersdelight.org/>`_\ . + + +See Also +-------- + +- :ref:`Boolean operations <lang-boolean>` (``&&``, ``||``) +- :ref:`Compound bitwise operations <lang-compoundbitwise>` (``&=``, + ``|=``, ``^=``). + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/boolean.rst b/docs/source/lang/cpp/boolean.rst new file mode 100644 index 0000000..f09345e --- /dev/null +++ b/docs/source/lang/cpp/boolean.rst @@ -0,0 +1,90 @@ +.. highlight:: cpp + +.. _lang-boolean: + +Boolean Operators +================= + +These can be used inside the condition of an :ref:`if <lang-if>` +statement. Evaluate to :ref:`true <lang-constants-true>` or +:ref:`false <lang-constants-false>`. + +.. contents:: Contents + :local: + +.. _lang-boolean-and: + +&& (logical and) +---------------- + +True only if both operands are true. For example:: + + if (digitalRead(2) == HIGH && digitalRead(3) == HIGH) { // read two switches + // ... + } + +is true only if both inputs are high. Another example:: + + if (a >= 10 && a <= 20){} // true if a is between 10 and 20 + +**Be careful** not to say ``10 <= a <= 20``! This won't work the way +you want. You have to separately test whether ``a`` is at least 10 +using ``a >= 10``, then test whether ``a`` is at most 20 using ``a <= +20``, then combine the results using ``&&``. + + +.. _lang-boolean-or: + +\|\| (logical or) +----------------- + +True if either operand is true. For example:: + + if (x > 0 || y > 0) { + // ... + } + +is true if either ``x`` or ``y`` is greater than 0. + +.. _lang-boolean-not: + +! (logical not) +--------------- + +True if the operand is false. For example:: + + if (!x) { + // ... + } + +is true if ``x`` is false (i.e. if ``x`` is zero). + +Some Advice +----------- + +.. warning:: + + Make sure you don't mistake the boolean AND operator ``&&`` + (double ampersand) for the :ref:`bitwise AND operator + <lang-bitwisemath-and>` ``&`` (single ampersand). They are + entirely different beasts. + + Similarly, do not confuse the boolean OR operator ``||`` (double + pipe) with the :ref:`bitwise OR operator <lang-bitwisemath-or>` + ``|`` (single pipe). + + The :ref:`bitwise NOT operator <lang-bitwisemath-not>` ``~`` + (tilde) looks much different than the boolean not operator ``!`` + (exclamation point, or "bang", as some programmers say), but you + still have to be sure which one you want. + + +See Also +-------- + +- :ref:`Bitwise operators <lang-bitwisemath>` (``&``, ``|``, ``^``, ``~``) +- :ref:`Compound bitwise operators <lang-compoundbitwise>` (``&=``, + ``|=``, ``^=``). +- :ref:`if statement <lang-if>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/booleanvariables.rst b/docs/source/lang/cpp/booleanvariables.rst new file mode 100644 index 0000000..e032c74 --- /dev/null +++ b/docs/source/lang/cpp/booleanvariables.rst @@ -0,0 +1,47 @@ +.. highlight:: cpp + +.. _lang-booleanvariables: + +Booleans +======== + +A **boolean** holds one of two values, :ref:`true +<lang-constants-true>` or :ref:`false <lang-constants-false>`. On a +Maple, each boolean variable has type ``bool``. + +.. warning:: + + On an Arduino, the type ``boolean`` is also provided. While the + Maple also has this type for compatibility, **its use is strongly + discouraged**. The ``bool`` type is a standard part of C++, while + ``boolean`` is a non-standard extension that serves no purpose. + +Example +------- + +:: + + // running is a boolean variable: + bool running = false; + + void setup() { + pinMode(BOARD_LED_PIN, OUTPUT); + pinMode(BOARD_BUTTON_PIN, INPUT); + } + + void loop() { + if (isButtonPressed()) { + // button is pressed + running = !running; // toggle running variable + digitalWrite(BOARD_LED_PIN, running) // indicate via LED + } + } + +See Also +-------- + +- :ref:`Boolean constants <lang-constants-bool>` +- :ref:`Boolean operators <lang-boolean>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/break.rst b/docs/source/lang/cpp/break.rst new file mode 100644 index 0000000..f367b99 --- /dev/null +++ b/docs/source/lang/cpp/break.rst @@ -0,0 +1,32 @@ +.. highlight:: cpp + +.. _lang-break: + +``break`` +========= + +``break`` is used to exit from a :ref:`while <lang-while>`\ , +:ref:`for <lang-for>`\ , or :ref:`do/while <lang-dowhile>` loop, +bypassing the normal loop condition. It is also used to exit from a +:ref:`switch <lang-switchcase>` statement. + + +Example +------- + +:: + + for (x = 0; x < 255; x ++) + { + digitalWrite(PWMpin, x); + sens = analogRead(sensorPin); + if (sens > threshold){ // bail out on sensor detect + x = 0; + // this line of code means that we'll immediately exit + // from the "for" loop: + break; + } + delay(50); + } + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/built-in-types.rst b/docs/source/lang/cpp/built-in-types.rst new file mode 100644 index 0000000..f14dce5 --- /dev/null +++ b/docs/source/lang/cpp/built-in-types.rst @@ -0,0 +1,108 @@ +.. highlight:: cpp + +.. _lang-built-in-types: + +================ + Built-in Types +================ + +This document serves as a reference for many of the built-in types +which are available when programming in the IDE. Programmers using +the :ref:`command-line tools <unix-toolchain>` will have access to +these types as long as they have imported `wirish.h +<https://github.com/leaflabs/libmaple/blob/master/wirish/wirish.h>`_; +several are defined in in `libmaple_types.h +<https://github.com/leaflabs/libmaple/blob/master/libmaple/libmaple_types.h>`_. + +.. _lang-built-in-types-integral: + +Integral types +-------------- + +.. cpp:type:: char + + 8-bit integer value. + +.. cpp:type:: short + + 16-bit integer value. + +.. cpp:type:: int + + 32-bit integer value. + +.. cpp:type:: long + + 32-bit integer value. + +.. cpp:type:: long long + + 64-bit integer value. + +.. cpp:type:: int8 + + 8-bit integer value. Synonym for ``signed char``. + +.. cpp:type:: uint8 + + 8-bit unsigned integer value. Synonym for ``unsigned char``. + +.. cpp:type:: byte + + 8-bit unsigned integer value. Synonym for ``unsigned char``. + +.. cpp:type:: int16 + + 16-bit integer value. Synonym for ``short``. + +.. cpp:type:: uint16 + + 16-bit unsigned integer value. Synonym for ``unsigned short``. + +.. cpp:type:: int32 + + 32-bit integer value. Synonym for ``int``. + +.. cpp:type:: uint32 + + Unsigned 32-bit integer value. Synonym for ``unsigned int`` + +.. cpp:type:: int64 + + 64-bit integer value. Synonym for ``long long`` + +.. cpp:type:: uint64 + + Unsigned 64-bit integer value. Synonym for ``unsigned long long``. + +Floating-Point Types +-------------------- + +.. cpp:type:: float + + 32-bit, IEEE-754 single-precision floating-point type. + +.. cpp:type:: double + + 64-bit, IEEE-754 double-precision floating-point type. + +Miscellaneous Types +------------------- + +.. cpp:type:: voidFuncPtr + + Pointer to a function that takes no arguments and returns nothing, i.e. :: + + typedef void (*voidFuncPtr)(void); + +.. cpp:type:: bool + + Boolean type. + +Other +----- + +.. cpp:type:: void + + Not really a type. To be honest with you, this only exists here to + silence warnings from our documentation build system. diff --git a/docs/source/lang/cpp/byte.rst b/docs/source/lang/cpp/byte.rst new file mode 100644 index 0000000..4634594 --- /dev/null +++ b/docs/source/lang/cpp/byte.rst @@ -0,0 +1,33 @@ +.. highlight:: cpp + +.. _lang-byte: + +byte +==== + +The ``byte`` type stores a 1-byte (8-bit) unsigned integer number, +from 0 to 255. + +.. warning:: + + The ``byte`` type is provided for compatibility with Arduino. + However, it is a non-standard extension. The standard C++ type for + storing an 8-bit unsigned integer is ``unsigned char``; we + recommend using that instead. (Your code will still work on an + Arduino). + + +Example +------- + +:: + + byte b = 134; + +See Also +-------- + +- :ref:`byte() <lang-bytecast>` (casting a value to a byte) +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/bytecast.rst b/docs/source/lang/cpp/bytecast.rst new file mode 100644 index 0000000..24c3b9e --- /dev/null +++ b/docs/source/lang/cpp/bytecast.rst @@ -0,0 +1,44 @@ +.. highlight:: cpp + +.. _lang-bytecast: + +byte() (cast) +============= + +Converts a value to the :ref:`byte <lang-byte>` data type. + +.. note:: + + Casting to the byte type is provided for compatibility with + Arduino. However, the recommended Maple type for storing an 8-bit + unsigned integer is ``uint8``. (C and C++ programmers: ``stdint.h`` + is also available). + + In order to cast a variable ``x`` to a ``uint8``, the + following syntax can be used:: + + uint8(x); + +Syntax +------ + +``byte(x)`` + +Parameters +---------- + +**x**: a value of any integer type + +Returns +------- + +The value, converted to a ``byte``. Note, however, that if the value +is larger than the maximum value you can store in a byte (255), then +the results might be strange and unexpected. + +See Also +-------- + +- :ref:`lang-byte` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/cc-attribution.txt b/docs/source/lang/cpp/cc-attribution.txt new file mode 100644 index 0000000..e100140 --- /dev/null +++ b/docs/source/lang/cpp/cc-attribution.txt @@ -0,0 +1,9 @@ +.. Included in all this directory's files in order to satisfy the +.. Arduino CC Attribution-ShareAlike 3.0 License + +.. admonition:: License and Attribution + + This documentation page was adapted from the `Arduino Reference + Documentation <http://arduino.cc/en/Reference/HomePage>`_\ , which + is released under a `Creative Commons Attribution-ShareAlike 3.0 + License <http://creativecommons.org/licenses/by-sa/3.0/>`_. diff --git a/docs/source/lang/cpp/char.rst b/docs/source/lang/cpp/char.rst new file mode 100644 index 0000000..686c0d1 --- /dev/null +++ b/docs/source/lang/cpp/char.rst @@ -0,0 +1,44 @@ +.. highlight:: cpp + +.. _lang-char: + +``char`` +======== + +The ``char`` type stores a 1-byte character value (or integer with +value from -128 to 127). Character literals are written in single +quotes, like this: ``'A'`` (for multiple characters - strings - use +double quotes: ``"ABC"``). + +Just like everything else on a computer, characters are stored as +numbers. You can see the specific encoding in the `ASCII chart +<http://en.wikipedia.org/wiki/ASCII#ASCII_printable_characters>`_\ +. This means that it is possible to do arithmetic on characters, in +which the ASCII value of the character is used (e.g. ``'A' + 1`` has the +decimal value 66, since the ASCII value of the capital letter A in +decimal is 65). See the :ref:`Serial.println() +<lang-serial-println>` documentation for more information about how +characters are converted into numbers. + +The ``char`` datatype is a signed type, meaning that it encodes +numbers from -128 to 127. For an unsigned type, which stores values +from 0 to 255, just use the type ``unsigned char`` (two words). + +Example +------- + +:: + + // The following two lines are equivalent, using the ASCII + // character encoding: + char c = 'A'; + char c = 65; + +See Also +-------- + +- :ref:`lang-int` +- :ref:`lang-array` (a string is just an array of ``char``\ s) +- :ref:`Serial.println() <lang-serial-println>` + +.. include:: cc-attribution.txt diff --git a/docs/source/lang/cpp/charcast.rst b/docs/source/lang/cpp/charcast.rst new file mode 100644 index 0000000..640ad85 --- /dev/null +++ b/docs/source/lang/cpp/charcast.rst @@ -0,0 +1,32 @@ +.. highlight:: cpp + +.. _lang-charcast: + +``char()`` (cast) +================= + +Converts a value to the :ref:`char <lang-char>` data type. + +Syntax +------ + +``char(x)`` + +Parameters +---------- + +**x**: a value of any type + +Returns +------- + +The value, converted to a ``char``. Note, however, that if the value +is outside the range of a ``char`` (-128 to 127), then the results +might be strange and unexpected. + +See Also +-------- + +- :ref:`char <lang-char>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/comments.rst b/docs/source/lang/cpp/comments.rst new file mode 100644 index 0000000..1428dc3 --- /dev/null +++ b/docs/source/lang/cpp/comments.rst @@ -0,0 +1,64 @@ +.. highlight:: cpp + +.. _lang-comments: + +Comments +======== + +Comments are lines in the program that are used to inform yourself or +others about the way the program works. They are ignored by the +compiler, and not exported to the processor, so they don't take up any +space in RAM or Flash. + +One use for comments is to help you understand (or remember) how your +program works, or to inform others how your program works. There are +two different ways of making comments. + +.. _lang-comments-singleline: + +**Single line comment**: Anything following two slashes, ``//``, until +the end of the line, is a comment:: + + x = 5; // the rest of this line is a comment + +.. _lang-comments-multiline: + +**Multi-line comment**: Anything in between a pair of ``/*`` and ``*/`` +is a comment:: + + /* <-- a slash-star begins a multi-line comment + + all of this in the multi-line comment - you can use it to comment + out whole blocks of code + + if (gwb == 0){ // single line comment is OK inside a multi-line comment + x = 3; + } + + // don't forget the "closing" star-slash - they have to be balanced: + */ + +Note that it's okay to use single-line comments within a multi-line +comment, but you can't use multi-line comments within a multi-line +comment. Here's an example:: + + /* ok, i started a multi-line comment + + x = 3; /* this next star-slash ENDS the multi-line comment: */ + + x = 4; // this line is outside of the multi-line comment + + // next line is also outside of the comment, and causes a compile error: + */ + +Programming Tip +--------------- + +When experimenting with code, "commenting out" parts of your program +is a convenient way to remove lines that may be buggy. This leaves +the lines in the code, but turns them into comments, so the compiler +just ignores them. This can be especially useful when trying to locate +a problem, or when a program refuses to compile and the compiler error +is cryptic or unhelpful. + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/comparison.rst b/docs/source/lang/cpp/comparison.rst new file mode 100644 index 0000000..9cd0a9f --- /dev/null +++ b/docs/source/lang/cpp/comparison.rst @@ -0,0 +1,86 @@ +.. highlight:: cpp + +.. _lang-comparison: + +Comparison Operators (``==``, ``!=``, ``<``, ``>``, ``<=``, ``>=``) +=================================================================== + +The comparison operators ``==``, ``!=``, ``<``, ``>``, ``<=``, and +``>=`` are used to compare two numbers. They are :ref:`true +<lang-constants-true>` when the comparison is true, and :ref:`false +<lang-constants-false>` otherwise. They are based on the symbols +=, ≠, <, >, ≤, and ≥ from mathematics. + +Here are some examples, with their meaning in comments:: + + // "eq" is true when x is equal to y + bool eq = (x == y); + + // "neq" is true when x is different than y + bool neq = (x != y); + + // "lt" is true when x is less than, but NOT equal to, y + bool lt = (x < y); + + // "gt" is true when x is greater than, but NOT equal to, y + bool gt = (x > y); + + // "lte" is true when x is less than or equal to y + bool lte = (x <= y); + + // "gte" is true when x is greater than or equal to y + bool gte = (x >= y); + +The parentheses are optional; they are present only for clarity. For +example, the following two lines are the same:: + + bool eq = x == y; + + bool eq = (x == y); + +Uses +---- + +Comparison operators, along with :ref:`boolean operators +<lang-boolean>`, are useful inside the conditionals of :ref:`if +<lang-if>` statements. Here's one example:: + + if (x < 50) { + // only execute these lines if x is less than 50 + SerialUSB.println("delaying:"); + SerialUSB.println(x); + delay(x); + } + +.. warning:: + Beware of accidentally using the single equal sign (``=``) when you + meant to test if two numbers are equal (``==``). This is a common + mistake inside of ``if`` statement conditionals, e.g.:: + + // DON'T MAKE THIS MISTAKE + if (x = 10) { + // body + } + + The single equal sign is the assignment operator, and sets x to 10 + (puts the value 10 into the variable x). Instead use the double equal + sign (e.g. ``if (x == 10)``), which is the comparison operator, and + tests *whether* x is equal to 10 or not. The latter statement is only + true if x equals 10, but the former statement will always be true. + + This is because C evaluates the statement ``if (x=10)`` as follows: 10 + is assigned to x (remember that the single equal sign is the + :ref:`assignment operator <lang-assignment>`), so x now + contains 10. Then the 'if' conditional evaluates 10, which evaluates + to :ref:`true <lang-constants-true>`, since any non-zero number + evaluates to ``true``. + + Consequently, the conditional of an ``if`` statement like ``if (x = + 10) {...}`` will always evaluate to ``true``, and the variable x + will be set to 10, which is probably not what you meant. + + (This sometimes has uses, though, so just because an assignment + appears within a conditional doesn't mean it's automatically wrong. + Be careful to know what you mean.) + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/compoundarithmetic.rst b/docs/source/lang/cpp/compoundarithmetic.rst new file mode 100644 index 0000000..d70a43c --- /dev/null +++ b/docs/source/lang/cpp/compoundarithmetic.rst @@ -0,0 +1,43 @@ +.. highlight:: cpp + +.. _lang-compoundarithmetic: + +Compound Arithmetic Operators (``+=`` , ``-=``, ``*=``, ``/=``) +=============================================================== + +These oparators perform a mathematical operation on a variable with +another constant or variable. These operators are just a convenient +shorthand:: + + x += y; // equivalent to the expression x = x + y; + x -= y; // equivalent to the expression x = x - y; + x *= y; // equivalent to the expression x = x * y; + x /= y; // equivalent to the expression x = x / y; + +Here is an example:: + + int x = 2; + int y = 10; + + x += 4; // x now contains 6 + x -= 3; // x now contains 3 + x *= y; // x now contains 30 + x /= 2; // x now contains 15 + x += max(20, 6); // x now contains 35 + x -= sq(5); // x now contains 15 + +Parameters +---------- + +**x**: a numeric variable + +**y**: a numeric variable, number constant, or any other expression +that evaluates to a number (e.g. call to a function that returns a +number). + +See Also +-------- + +- :ref:`Arithmetic operators <lang-arithmetic>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/compoundbitwise.rst b/docs/source/lang/cpp/compoundbitwise.rst new file mode 100644 index 0000000..4efe5df --- /dev/null +++ b/docs/source/lang/cpp/compoundbitwise.rst @@ -0,0 +1,229 @@ +.. highlight:: cpp + +.. _lang-compoundbitwise: + +Compound Bitwise Operators (``&=``, ``|=``, ``^=``) +=================================================== + +The compound bitwise operators perform their calculations at the +bit level of variables. They are often used to clear and set +specific bits of a variable. + +See the :ref:`bitwise math tutorial <lang-bitwisemath>` for more +information on bitwise operators. + +.. contents:: Contents + :local: + +.. _lang-compoundbitwise-and: + +Compound bitwise AND (``&=``) +----------------------------- + +The compound bitwise AND operator ``&=`` is often used with a variable +and a constant to force particular bits in a variable to be zero. This +is often referred to in programming guides as "clearing" or +"resetting" bits. In a program, writing the line ``x &= y;`` is +equivalent to writing ``x = x & y;``. That is, the value of ``x`` +after the line will be equal to its old value bitwise ANDed with the +value of ``y``:: + + x &= y; // equivalent to x = x & y; + +You can use any integer variable for ``x`` (i.e., any variable of type +``int``, ``char``, ``byte``, ``long long``, etc.). You can use either +an integer variable or any :ref:`integer value +<lang-constants-integers>` (like ``3`` or ``0x20``) for ``y``. + +Before doing an example of ``&=``, let's first review the Bitwise AND +(``&``) operator:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 0 0 1 (operand1 & operand2) = result + +As shown above, bits that are "bitwise ANDed" with 0 become 0, while +bits that are "bitwise ANDed" with 1 are left unchanged. So, if ``b`` +is a ``byte`` variable, then ``b & B00000000`` equals zero, and ``b & +B11111111`` equals ``b``. + +.. _lang-compoundbitwise-binconst: + +.. note:: The above uses :ref:`binary constants + <lang-constants-integers-bin>`\ . The numbers are still the same + value in other representations, they just might not be as easy to + understand. + + Normally, in C and C++ code, :ref:`hexadecimal + <lang-constants-integers-hex>` or :ref:`octal + <lang-constants-integers-oct>` are used when we're interested in + an integer's bits, rather than its value as a number. + + While hexadecimal and octal literals might be harder to understand + at first, you should really take the time to learn them. They're + part of C, C++, and many other programming languages, while binary + constants are available only for compatibility with Arduino. + + Also, ``B00000000`` is shown for clarity, but zero in any number + format is zero. + +So, to clear (set to zero) bits 0 and 1 of a one-byte variable, while +leaving the rest of the variable's bits unchanged, use the compound +bitwise AND operator ``&=`` with the constant ``B11111100`` +(hexadecimal ``0xFC``\ ):: + + 1 0 1 0 1 0 1 0 variable + 1 1 1 1 1 1 0 0 mask + ---------------------- + 1 0 1 0 1 0 0 0 + ^^^^^^^^^^^^^^^^ ^^^^ + unchanged cleared + + +Here is the same representation with the variable's bits replaced +with the symbol ``x``\ :: + + x x x x x x x x variable + 1 1 1 1 1 1 0 0 mask + ---------------------- + x x x x x x 0 0 + ^^^^^^^^^^^^^^^^ ^^^^ + unchanged cleared + + +So, using a byte variable ``b``\ , if we say:: + + b = B10101010; // B10101010 == 0xAA + b &= B11111100; // B11111100 == 0xFC + +then we will have :: + + b == B10101000; // B10101000 == 0xA8 + +.. _lang-compoundbitwise-or: + +Compound bitwise OR (``|=``) +---------------------------- + +The compound bitwise OR operator ``|=`` is often used with a variable +and a constant to "set" (set to 1) particular bits in a variable. In +a program, writing the line ``x |= y;`` is equivalent to writing ``x = +x | y;``. That is, the value of ``x`` after the line will be equal to +its old value bitwise ORed with the value of ``y``:: + + x |= y; // equivalent to x = x | y; + +You can use any integer variable for ``x`` (i.e., any variable of type +``int``, ``char``, ``long long`` etc.). You can use either an integer +variable or any integer value (like ``3`` or ``0x20``) for ``y``. +(This works the same way as :ref:`compound bitwise AND +<lang-compoundbitwise-and>`\ , ``&=``). + +Before doing an example of ``|=``, let's first review the Bitwise OR +(``|``) operator:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 1 1 1 (operand1 | operand2) = result + +Bits that are "bitwise ORed" with 0 are unchanged, while bits that are +"bitwise ORed" with 1 are set to 1. So if ``b`` is a ``byte`` +variable, then ``b | B00000000`` equals ``b``, and ``b & B11111111`` +equals ``B11111111`` (here we've used binary constants; see the +:ref:`note <lang-compoundbitwise-binconst>` above). + +So, to set bits 0 and 1 of a one-byte variable, while leaving the rest +of the variable unchanged, use the compound bitwise OR operator +(``|=``) with the constant ``B00000011`` (hexadecimal ``0x3``):: + + 1 0 1 0 1 0 1 0 variable + 0 0 0 0 0 0 1 1 mask + ---------------------- + 1 0 1 0 1 0 1 1 + ^^^^^^^^^^^^^^^^ ^^^^ + unchanged set + +Here is the same representation with the variable's bits replaced with +the symbol ``x``:: + + x x x x x x x x variable + 0 0 0 0 0 0 1 1 mask + ---------------------- + x x x x x x 1 1 + ^^^^^^^^^^^^^^^^ ^^^^ + unchanged set + +So, using a byte variable ``b``, if we say:: + + b = B10101010; // B10101010 == 0xAA + b |= B00000011; // B00000011 == 0x3 + +then we will have :: + + b == B10101011; // B10101011 == 0xAB + +.. _lang-compoundbitwise-xor: + +Compound bitwise XOR (``^=``) +----------------------------- + +The compound bitwise XOR operator ``^=`` is used with a variable and a +constant to "toggle" (change 0 to 1, and 1 to 0) particular bits in a +variable. In a program, writing the line ``x ^= y;`` is equivalent to +writing ``x = x ^ y;``. That is, the value of ``x`` after the line +will be equal to its old value bitwise XORed with the value of ``y``:: + + x ^= y; // equivalent to x = x ^ y; + +You can use any integer variable for ``x`` (i.e., any variable of type +``int``, ``char``, ``long long``, etc.). You can use either an +integer variable or any integer value (like ``3`` or ``0x20``) for +``y``. (This works the same way as :ref:`&= +<lang-compoundbitwise-and>` and :ref:`\|= <lang-compoundbitwise-or>`; +in fact, these three operators all work the same in this way). + +Before doing an example of ``^=``, let's first review the Bitwise +XOR operator, ``^``:: + + 0 0 1 1 operand1 + 0 1 0 1 operand2 + ---------- + 0 1 1 0 (operand1 ^ operand2) = result + +One way to look at bitwise XOR is that each bit in the result is a 1 +if the input bits are different, or 0 if they are the same. Another +way to think about it is that the result bit will be 1 when *exactly* +one (no more, no less) of the input bits is 1; otherwise, it will be +zero. This means that if you XOR a bit with 1, it will change (or +toggle) its value, while if you XOR a bit with 0, it stays the same. + +So, to toggle bits 0 and 1 of a one-byte variable, while leaving the +rest of the variable unchanged, use the compound bitwise XOR operator +``^=`` with the constant ``B00000011`` (hexadecimal ``0x3``\ ; see +:ref:`note <lang-compoundbitwise-binconst>` above):: + + 1 0 1 0 1 0 1 0 variable + 0 0 0 0 0 0 1 1 mask + ---------------------- + 1 0 1 0 1 0 1 1 + ^^^^^^^^^^^^^^^^ ^^^^ + unchanged toggled + +So, using a byte variable ``b``, if we say:: + + b = B10101010; // B10101010 == 0xAA + b ^= B00000011; // B00000011 == 0x3 + +then we will have :: + + b == B10101001; // B10101001 == 0xA9 + +See Also +-------- + +- :ref:`Boolean operations <lang-boolean>` (``&&``, ``||``) +- :ref:`Bitwise operators <lang-bitwisemath>` (``&``, ``|``, ``^``, ``~``) + +.. include:: cc-attribution.txt diff --git a/docs/source/lang/cpp/const.rst b/docs/source/lang/cpp/const.rst new file mode 100644 index 0000000..ad0c580 --- /dev/null +++ b/docs/source/lang/cpp/const.rst @@ -0,0 +1,50 @@ +.. highlight:: cpp + +.. _lang-const: + +``const`` +========= + +The ``const`` keyword stands for "constant". It is a variable +*qualifier* that modifies the behavior of the variable, making a +variable "*read-only*". This means that the variable can be used just +as any other variable of its type, but its value cannot be +changed. You will get a compiler error if you try to assign a value to +a ``const`` variable. + +Constants defined with the ``const`` keyword obey the same rules of +:ref:`variable scoping <lang-scope>` that govern other +variables. This, and the pitfalls of using :ref:`#define +<lang-define>`, often makes using the ``const`` keyword a superior +method for defining constants than ``#define``. + +Example +------- + + :: + + // this defines a variable called "pi", which cannot be changed: + const float pi = 3.14; + float x; + + // .... + + x = pi * 2; // it's fine to find the value of a const variable + + pi = 7; // illegal - you can't write to (modify) a constant + +**#define** or **const** +------------------------ + +You can use either ``const`` or ``#define`` for creating numeric or +string constants. For :ref:`arrays <lang-array>`\ , you will need +to use ``const``. In general, ``const`` is preferred over ``#define`` +for defining constants. + +See Also +-------- + +- :ref:`#define <lang-define>` +- :ref:`volatile <lang-volatile>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/continue.rst b/docs/source/lang/cpp/continue.rst new file mode 100644 index 0000000..2a694f6 --- /dev/null +++ b/docs/source/lang/cpp/continue.rst @@ -0,0 +1,30 @@ +.. highlight:: cpp + +.. _lang-continue: + +``continue`` +============ + +The ``continue`` keyword skips the rest of the current iteration of a +:ref:`while <lang-while>`\ , :ref:`for <lang-for>`\ , or +:ref:`do/while <lang-dowhile>` loop. It continues by checking the +conditional expression of the loop, and proceeding with any subsequent +iterations. + +Example +------- + +:: + + + for (x = 0; x < 255; x ++) { + if (x > 40 && x < 120) { // create jump in values + continue; // skips the next two lines and goes to the + // beginning of the loop, with the next value of x + } + + digitalWrite(PWMpin, x); + delay(50); + } + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/curly-braces.rst b/docs/source/lang/cpp/curly-braces.rst new file mode 100644 index 0000000..df2fe2a --- /dev/null +++ b/docs/source/lang/cpp/curly-braces.rst @@ -0,0 +1,106 @@ +.. highlight:: cpp + +.. _lang-curly-braces: + +Curly Braces (``{``, ``}``) +=========================== + +.. contents:: Contents + :local: + +Introduction +------------ + +Curly braces (also referred to as just "braces" or as "curly +brackets") are a major part of the C and C++ programming +languages. They are used in several different constructs, outlined +below, and this can sometimes be confusing for beginners. + +An opening curly brace, ``{`` must always be followed by a closing +curly brace ``}``. This is a condition that is often referred to as +the braces being *balanced*. The Maple IDE (integrated development +environment) includes a convenient feature to check the balance of +curly braces. Just select a brace, or even click the insertion point +immediately following a brace, and its companion will be highlighted\ +[#fbug]_\ . + +Beginning programmers, and programmers coming to C++ from languages +without braces, often find using them confusing or daunting. + +Because the use of the curly brace is so varied, it is good +programming practice to type the closing brace immediately after +typing the opening brace when inserting a construct which requires +curly braces. Then insert some blank lines between your braces and +begin inserting statements. Your braces, and your attitude, will never +become unbalanced. + +Unbalanced braces can often lead to cryptic, impenetrable compiler +errors that can sometimes be hard to track down in a large program. +Because of their varied usages, braces are also incredibly important +to the syntax of a program and moving a brace one or two lines will +usually dramatically affect the meaning of a program. + +The main uses of curly braces +----------------------------- + +**Functions**:: + + // a function body needs braces around it + void myFunction(datatype argument) { + // ... function body goes in here ... + } + +**Loops** (see the :ref:`while <lang-while>`\ , :ref:`for +<lang-for>`\ , and :ref:`do/while <lang-dowhile>` loop reference +pages for more information):: + + // you should put braces around the body of a loop: + + while (boolean expression) { + // code inside the loop goes here + } + + for (initialisation; termination condition; incrementing expr) { + // code inside the loop goes here + } + + do { + // code inside the loop goes here + } while (boolean expression); + + +**Conditional statements** (see the :ref:`if statement <lang-if>` +reference page for more information):: + + // you should put braces around the body of an "if", "else if", + // or "else": + + if (boolean expression) { + // code inside the "if" + } + else if (boolean expression) { + // code inside the "else if" + } + else { + // code inside the "else" + } + +**Switch statements** (see the :ref:`switch statement +<lang-switchcase>` reference page for more information):: + + switch (var) { + case 1: + doThing1(); + break; + case 2: + doThing2(); + break; + } + +.. rubric:: Footnotes + +.. [#fbug] At present this feature is slightly buggy as the IDE will + often find (incorrectly) a brace in text that has been commented + out. + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/define.rst b/docs/source/lang/cpp/define.rst new file mode 100644 index 0000000..b22085f --- /dev/null +++ b/docs/source/lang/cpp/define.rst @@ -0,0 +1,54 @@ +.. highlight:: cpp + +.. _lang-define: + +``#define`` +=========== + +``#define`` is a useful C and C++ feature that allows the programmer +to give a name to a constant value before the program is compiled. +The compiler will replace references to these constants with the +defined value at compile time. + +This can have some unwanted side effects. In general, the :ref:`const +<lang-const>` keyword is preferred for defining constants. + +Syntax +------ + +The following line would define the name ``MY_CONSTANT`` to have value +``value``:: + + #define MY_CONSTANT value + +Note that the ``#`` is necessary. It is usually good style for the +name to be capitalized, although this is not required. + +There is no semicolon after the #define statement. If you include one, +the compiler will likely throw cryptic errors in unrelated places. +That is, **don't do this**:: + + // DON'T DO THIS! THE SEMICOLON SHOULDN'T BE THERE! + #define NAME value; + +Similarly, including an equal sign after the ``#define`` line will +also generate a cryptic compiler error further down the page. That +is, **don't do this, either**:: + + // DON'T DO THIS, EITHER! THE EQUALS SIGN SHOULDN'T BE THERE! + #define NAME = value + +Example +------- + + :: + + #define MAPLE_LED_PIN 13 + // The compiler will replace any mention of MAPLE_LED_PIN with + // the value 13 at compile time. + +See Also +-------- +- :ref:`const <lang-const>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/double.rst b/docs/source/lang/cpp/double.rst new file mode 100644 index 0000000..59422eb --- /dev/null +++ b/docs/source/lang/cpp/double.rst @@ -0,0 +1,46 @@ +.. _lang-double: + +``double`` +========== + +Double precision floating point type. Occupies 8 bytes. On Maple, the +``double`` type has a range of approximately -1.79769×10^308 to +1.79769×10^308; the ``double`` type subject to the same :ref:`overflow +issues <lang-variables-rollover>` as any numeric data type. + +Floating point numbers are not exact, and may yield strange results +when compared. For example ``6.0 / 3.0`` may not equal ``2.0``. You +should instead check that the absolute value of the difference between +the numbers is less than some small number. + +Floating point math is also much slower than integer math in +performing calculations, so should be avoided if, for example, a loop +has to run at top speed for a critical timing function. Programmers +often go to some lengths to convert floating point calculations to +integer math to increase speed. + +For more information, see the `Wikipedia article on floating point +math <http://en.wikipedia.org/wiki/Floating_point>`_\ . + +Floating-point numbers represent numbers with "decimal point", unlike +integral types, which always represent whole numbers. Floating-point +numbers are often used to approximate analog and continuous values +because they have greater resolution than integers. + +The double implementation on the Maple uses twice the number of bytes +as a :ref:`float <lang-float>`, with the corresponding gains in +precision. + +Tip +--- + +Users who borrow code from other sources that includes ``double`` +variables may wish to examine the code to see if the implied range and +precision are different from that actually achieved on the Maple. + +See Also +-------- + +- :ref:`float <lang-float>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/doublecast.rst b/docs/source/lang/cpp/doublecast.rst new file mode 100644 index 0000000..d3f32ce --- /dev/null +++ b/docs/source/lang/cpp/doublecast.rst @@ -0,0 +1,27 @@ +.. highlight:: cpp + +.. _lang-doublecast: + +``double()`` (cast) +=================== + +Converts a value to the :ref:`double <lang-double>` floating point +data type. Here is an example:: + + int x = 2; + double d = double(x); // d now holds 2.0, a double value + +The value ``x`` can be of any type. However, if ``x`` is not a number +(like an ``int`` or ``long long``), you will get strange results. + +See the :ref:`double <lang-double>` reference for details about the +precision and limitations of ``double`` values on the Maple. + +See Also +-------- + +- :ref:`double <lang-double>` +- :ref:`float <lang-float>` +- :ref:`float() <lang-floatcast>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/dowhile.rst b/docs/source/lang/cpp/dowhile.rst new file mode 100644 index 0000000..d229122 --- /dev/null +++ b/docs/source/lang/cpp/dowhile.rst @@ -0,0 +1,26 @@ +.. highlight:: cpp + +.. _lang-dowhile: + +``do``/``while`` +================ + +A ``do`` loop works in the same manner as a :ref:`while +<lang-while>` loop, with the exception that the condition is tested +at the end of the loop, so the ``do`` loop will *always* run at least +once. + +This is the basic syntax:: + + do { + // statement block + } while (test condition); + +Example:: + + do { + delay(50); // wait for sensors to stabilize + x = readSensors(); // check the sensors + } while (x < 100); + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/enum.rst b/docs/source/lang/cpp/enum.rst new file mode 100644 index 0000000..b6409eb --- /dev/null +++ b/docs/source/lang/cpp/enum.rst @@ -0,0 +1,52 @@ +.. highlight:: cpp + +.. _lang-enum: + +``enum`` +======== + +The ``enum`` keyword is used to specify an enumeration type. An +enumeration type is a type whose values are taken from a specified, +fixed list of constant values. + +Example +------- + +Here's an example defining an enumeration type called ``weather``, +which has values ``HOT``, ``COMFY``, and ``COLD``:: + + enum weather {HOT, COMFY, COLD}; + +Once you've defined this type, you can create variables of type +``weather``, in the same way you would with an :ref:`int <lang-int>`:: + + // create a weather variable named theWeather, with value COMFY: + weather theWeather = COMFY; + +Enumeration types are useful within :ref:`switch statements +<lang-switchcase>`. If you know that an argument is of an enumeration +type, you can make ``case`` statements for all of that type's possible +values, so you know you won't miss anything:: + + void describeWeather(weather currentWeather) { + switch(currentWeather) { + case HOT: + SerialUSB.println("it's hot out"); + break; + case COMFY: + SerialUSB.println("it's nice today"); + break; + case COLD: + SerialUSB.println("it's freezing!"); + break; + } + } + +Such a ``switch`` statement would need no :ref:`default +<lang-switchcase-default>`, since we know that ``currentWeather`` must +be either ``HOT``, ``COMFY``, or ``COLD``. + +See Also +-------- + +- :ref:`lang-switchcase` diff --git a/docs/source/lang/cpp/float.rst b/docs/source/lang/cpp/float.rst new file mode 100644 index 0000000..5195fac --- /dev/null +++ b/docs/source/lang/cpp/float.rst @@ -0,0 +1,50 @@ +.. highlight:: cpp + +.. _lang-float: + +``float`` +========= + +Single-precision floating point number. Occupies 4 bytes. On Maple, +the ``float`` type has a range of approximately -3.40282×10^38 to +3.40282×10^38; the ``float`` type is subject to the same +:ref:`overflow issues <lang-variables-rollover>` as any numeric data +type. + +``float``\ s have only 6-7 decimal digits of precision. That means the +total number of digits, not the number to the right of the decimal +point. You can get more precision by using a :ref:`double +<lang-double>` (which has a precision of about 16 decimal digits). + +The following example declares a ``float`` value named ``myfloat``:: + + float myfloat; + +This example declares a ``float`` value named ``sensorCalibrate``, +with value 1.117:: + + float sensorCalibrate = 1.117; + +The general syntax for declaring a float named ``var`` with value +``val`` is:: + + float var = val; + +Here is a more extended example involving a :ref:`float cast +<lang-floatcast>`:: + + int x; + int y; + float z; + + x = 1; + y = x / 2; // y now contains 0, ints can't hold fractions + z = float(x) / 2; // z now contains .5 + +See Also +-------- + +- :ref:`double <lang-double>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/floatcast.rst b/docs/source/lang/cpp/floatcast.rst new file mode 100644 index 0000000..af92543 --- /dev/null +++ b/docs/source/lang/cpp/floatcast.rst @@ -0,0 +1,28 @@ +.. highlight:: cpp + +.. _lang-floatcast: + +``float()`` (cast) +================== + +Converts a value to the :ref:`float <lang-float>` data type. Here is +an example (see the :ref:`constants reference <lang-constants-fp>` for +an explanation of the "2.0f"):: + + int x = 2; + float f = float(x); // f now holds 2.0f, a float value + +The value ``x`` can be of any type. However, if ``x`` is not a number +(like an ``int``), you will get strange results. + +See the :ref:`float <lang-float>` reference for details about the +precision and limitations of ``float`` values on the Maple. + +See Also +-------- + +- :ref:`float <lang-float>` +- :ref:`double <lang-double>` +- :ref:`double() <lang-doublecast>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/for.rst b/docs/source/lang/cpp/for.rst new file mode 100644 index 0000000..78ea562 --- /dev/null +++ b/docs/source/lang/cpp/for.rst @@ -0,0 +1,142 @@ +.. highlight:: cpp + +.. _lang-for: + +``for`` +======= + +A ``for`` loop is used to repeat a block of statements enclosed in +curly braces. ``for`` loops are useful for performing repetitive +operations, and are often used in combination with :ref:`arrays +<lang-array>` to operate on collections of data or multiple +:ref:`pins <gpio>`. A ``for`` loop is composed of two parts: first, a +*header*, which sets up the for loop, and then a *body*, which is made +up of lines of code enclosed in curly braces. + +.. contents:: Contents + :local: + +Syntax +------ + +There are three parts to the ``for`` loop header: an *initialization* +expression, *loop condition* expression, and a *post-loop* +expression. The general syntax looks like this:: + + for (initialization; condition; post-loop) { + // all of these lines inside the curly braces are part + // of the loop body. + statement 1; + statement 2; + ... + } + +(Note that there is no semicolon after the post-loop). The +initialization happens first and exactly once, before the loop begins. +Each time through the loop, the condition is tested. The condition is +a :ref:`boolean <lang-boolean>` expression. If it is true, then the +list of statements inside the curly braces are executed. Next, the +post-loop is executed. The loop then begins again by evaluating the +condition again, entering the loop body if it is true. This proceeds +until the condition becomes false. + +Examples +-------- + +Here's an example:: + + // Dim an LED using a PWM pin + int pwmPin = 9; // LED in series with 470 ohm resistor on pin 9 + + void setup() { + pinMode(pwmPin, PWM); + } + + void loop() { + for (int i=0; i <= 65535; i++) { + pwmWrite(pwmPin, i); + delay(1); + } + } + +There is a ``for`` loop In the :ref:`loop() <lang-loop>` function of +the above example. This loop starts by declaring an ``int`` variable +named ``i``, whose value starts out at zero. The loop proceeds by +checking if ``i`` is less than or equal to 65535. Since ``i`` is +zero, this is true, and so the calls to :ref:`pwmWrite() +<lang-pwmwrite>` and :ref:`delay() <lang-delay>` happen next. At this +point, the post-loop expression ``i++`` is evaluated, which +:ref:`increments <lang-increment>` ``i``, so that ``i`` becomes one. +That concludes the first time through the loop. Each "time through +the loop" is referred to as an *iteration*. + +The loop then jumps back to the beginning, checking the condition as +the beginning of its second iteration (initialization is skipped, +since this only happens once, before the first iteration). One is +less than 65535, so the loop statements are executed again. This +proceeds over and over until the iteration when ``i`` finally +reaches 65536. At that point, the condition is no longer true, so the +loop stops executing, and the ``loop()`` function returns. + +Here's another example, using a ``for`` loop to brighten and fade an +LED (see the :ref:`pwmWrite() <lang-pwmwrite>` reference for more +information):: + + int pwmPin = 9; // hook up the LED to pin 9 + void loop() { + int x = 1; + for (int i = 0; i >= 0; i += x) { + analogWrite(pwmPin, i); // controls the brightness of the LED + if (i == 65535) { + x = -1; // switch direction, so i starts decreasing + } + delay(1); + } + } + +Coding Tips +----------- + +The C ``for`` loop is more flexible than ``for`` loops found in some +other computer languages, including BASIC. Any or all of the three +header elements may be left blank, although the semicolons are +required. Also the statements for initialization, condition, and +post-loop can be any valid C statements, and use any C datatypes, +including :ref:`floating point numbers <lang-double>`. These types +of unusual ``for`` loops sometimes provide solutions to less-common +programming problems. + +For example, using a multiplication in the post-loop line will +generate a `geometric progression +<http://en.wikipedia.org/wiki/Geometric_progression>`_:: + + for(int x = 1; x <= 100; x = x * 2) { + SerialUSB.println(x); + } + + +This loop prints out the numbers 1, 2, 4, 8, ..., 64. Check +your understanding of ``for`` loops by answering the following two +questions (answers are in footnote [#fanswers]_\ ): + +1. How many iterations occur before the loop finishes? + +2. Why does it stop at 64? + +See Also +-------- + +- :ref:`while <lang-while>` loops +- :ref:`do <lang-dowhile>` loops + +.. rubric:: Footnotes + +.. [#fanswers] + 1. Seven. + + 2. After the seventh iteration, the post-loop causes ``x`` to + equal 128. This is larger than 100, so the loop condition is + false, and the loop stops. + + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/goto.rst b/docs/source/lang/cpp/goto.rst new file mode 100644 index 0000000..2c0b3b0 --- /dev/null +++ b/docs/source/lang/cpp/goto.rst @@ -0,0 +1,129 @@ +.. highlight:: cpp + +.. _lang-goto: + +Labels and ``goto`` +=================== + +A *label* gives a name to a line of code within a function. You can +label a line by writing a name for it, then a colon (``:``), before +the line starts. The ``goto`` keyword allows program flow to transfer +to a labeled line from anywhere within the same function. + +.. warning:: The use of ``goto`` is discouraged in C and C++ + programming. It is *never necessary* to use ``goto`` to write a + program. + + Unless you know what you're doing, using ``goto`` tends to + encourage code which is harder to debug and understand than + programs without ``goto`` that do the same thing. That said, + however, it's sometimes useful; :ref:`see below <goto-when-to-use>` + for a concrete example. + +Using Labels and goto +--------------------- + +Labels and ``goto`` are probably best explained through example. +Let's start with an example of how to label lines. The first line +(``int x = analogRead(some_pin);``) in the :ref:`loop <lang-loop>` +function below has label ``readpin``. The third line (``delay(x);``) +has label ``startdelay``. The second line (``SerialUSB.println(x);``) +does not have a label:: + + void loop() { + readpin: + int x = analogRead(some_pin); + SerialUSB.println(x); // for debugging + startdelay: + delay(x); + // ... more code ... + } + +Anything which can be a :ref:`variable <lang-variables>` name can +be a label. + +Let's say that we wanted to print ``x`` only if it was very large, say +at least 2000. We might want to do this just so anybody watching on a +:ref:`serial monitor <ide-serial-monitor>` would know they were in for +a longer wait than usual. We can accomplish this through the use of a +``goto`` statement that skips the printing if ``x`` is less than +2000:: + + void loop() { + readpin: + int x = analogRead(some_pin); + if (x < 2000) { + goto startdelay; + } + SerialUSB.println(x); // for debugging + startdelay: + delay(x); + // ... more code ... + } + +In this modified program, whenever ``x`` is less than 2000, the body +of the :ref:`if <lang-if>` statement in the second line is +executed. The ``goto`` statement inside the ``if`` body skips +straight to the line labeled ``startdelay``, passing over the line +doing the printing. + +A ``goto`` does not have to "move forwards"; it can go "backwards", +too. For example, the following program prints "5" forever (why?):: + + void loop() { + printfive: + SerialUSB.println(5); + goto printfive; + SerialUSB.println(6); + } + +.. _goto-when-to-use: + +When to Use goto +---------------- + +As mentioned above, use of ``goto`` is `generally discouraged +<http://en.wikipedia.org/wiki/Goto#Criticism_and_decline>`_. However, +when used with care, ``goto`` can simplify certain programs. One +important use case for ``goto`` is breaking out of deeply nested +:ref:`for <lang-for>` loops or :ref:`if <lang-if>` logic blocks. +Here's an example:: + + for(int r = 0; r < 255; r++) { + for(int g = 255; g > -1; g--) { + for(int b = 0; b < 255; b++) { + if (analogRead(0) > 250) { + goto bailout; + } + // more statements ... + } + // innermost loop ends here + } + } + bailout: + // more code here + +In the above example, whenever the :ref:`analog reading +<lang-analogread>` on pin 0 was greater than 250, the program would +jump to the line labeled ``bailout``, exiting all three loops at once. + +While there is already a :ref:`break <lang-break>` keyword for +breaking out of a loop, it will only break out of the *innermost* +loop. So, if instead of saying "``goto bailout;``", there was a +"``break;``" instead, the program would only exit from the loop with +header "``for(int b = 0; b < 255; b++)``". The program would continue +at the line which reads "``// innermost loop ends here``", which is +clearly undesirable if you wanted to leave all three loops at once. + +More examples of when ``goto`` is a good choice are given in Donald +Knuth's paper, "Structured Programming with go to Statements"; see +below for a link. + +See Also +-------- + +- Dijkstra, Edsger W. `Go To Statement Considered Harmful <http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.92.4846&rep=rep1&type=pdf>`_ (PDF) + +- Knuth, Donald. `Structured Programming with go to Statements <http://pplab.snu.ac.kr/courses/adv_pl05/papers/p261-knuth.pdf>`_ (PDF) + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/if.rst b/docs/source/lang/cpp/if.rst new file mode 100644 index 0000000..f248b05 --- /dev/null +++ b/docs/source/lang/cpp/if.rst @@ -0,0 +1,121 @@ +.. highlight:: cpp + +.. _lang-if: + +``if``/``else`` +=============== + +An ``if`` statement is used to execute code when certain conditions +are met. The general syntax for an ``if`` statement is:: + + if (condition) { + body + } + +An ``if`` statement first tests whether its *condition* is true (such +as an input being above a certain number). If the condition is true, +the ``if`` statement executes its *body*, which is made up of lines of +code inside :ref:`curly braces <lang-curly-braces>`. If the condition +is false, the body is not executed. Here's a more concrete example:: + + if (someVariable > 50) { + // do something here + } + +The program tests to see if ``someVariable`` is greater than 50. If it +is, the program executes every line in the curly braces (which in the +above example does nothing, since the body is just the :ref:`comment +<lang-comments>` line "``// do something here``"). + +Put another way, if the statement in parentheses is true, the +statements inside the braces are run. If not, the program skips over +the code. + +An ``if`` statement's condition (which is inside the parentheses after +``if``) often uses one or more :ref:`boolean <lang-boolean>` or +:ref:`comparison <lang-comparison>` operators. + +Writing the if Body +------------------- + +The brackets may be omitted after an ``if`` statement's +conditional. If this is done, the next line (which ends in a +semicolon) becomes the only line in the body. The following three +``if`` statements all do the same thing:: + + if (x > 120) digitalWrite(pin, HIGH); + + if (x > 120) + digitalWrite(pin, HIGH); + + if (x > 120) { + digitalWrite(pin, HIGH); + } + +However, the following two examples are different:: + + // example 1: two lines of code in the if body + if (x > 120) { + digitalWrite(pin1, HIGH); + digitalWrite(pin2, HIGH); + } + + // example 2: one line of code in the if body, and + // another line of code after the if statement + if (x > 120) + digitalWrite(pin1, HIGH); // this is in the if body + digitalWrite(pin2, HIGH); // this is NOT in the if body + +In the first example, since the body is enclosed in curly braces, both +lines are included. In the second example, since the curly braces are +missing, only the first line is in the ``if`` body. + +``else`` +-------- + +``if``/\ ``else`` allows greater control over the flow of code than +the basic :ref:`if <lang-if>` statement, by allowing multiple tests to +be grouped together. For example, an :ref:`analog input +<lang-analogread>` could be tested, with one action taken if the input +was less than 500, and another action taken if the input was 500 or +greater. The code would look like this:: + + if (pinFiveInput < 500) { + // action A + } else { + // action B + } + +``else`` can precede another ``if`` test, so that multiple, mutually +exclusive tests can be run at the same time. + +Each test will proceed to the next one until a true test is +encountered. When a true test is found, its associated block of code +is run, and the program then skips to the line following the entire +if/else construction. If no test proves to be true, the default +``else`` block is executed, if one is present, and sets the default +behavior. + +Note that an ``else if`` block may be used with or without a +terminating ``else`` block, and vice-versa. An unlimited number of +such ``else if`` branches is allowed. Here is a code example:: + + if (pinFiveInput < 500) { + // do Thing A + } else if (pinFiveInput >= 1000) { + // do Thing B + } else { + // do Thing C + } + +Another way to express branching, mutually exclusive tests, is with a +:ref:`switch/case <lang-switchcase>` statement. + + +See Also +-------- + +- :ref:`boolean operators <lang-boolean>` +- :ref:`comparison operators <lang-comparison>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/include.rst b/docs/source/lang/cpp/include.rst new file mode 100644 index 0000000..163509d --- /dev/null +++ b/docs/source/lang/cpp/include.rst @@ -0,0 +1,70 @@ +.. highlight:: cpp + +.. _lang-include: + +``#include`` +============ + +``#include`` is used to include outside libraries in your sketch. +This gives the programmer access to a large group of standard C +libraries (groups of pre-made functions and data types), and also +libraries written especially for Maple. + +Example +------- + +This example (from the `Arduino LiquidCrystal Tutorial +<http://arduino.cc/en/Tutorial/LiquidCrystal>`_) includes a library +that is used to control :ref:`LCD displays +<libraries-liquid-crystal>`:: + + // include the library code: + #include <LiquidCrystal.h> + + // initialize the library with the numbers of the interface pins + LiquidCrystal lcd(12, 11, 5, 4, 3, 2); + + void setup() { + // set up the LCD's number of columns and rows: + lcd.begin(16, 2); + // Print a message to the LCD. + lcd.print("hello, world!"); + } + + void loop() { + // set the cursor to column 0, line 1 + // (note: line 1 is the second row, since counting begins with 0): + lcd.setCursor(0, 1); + // print the number of seconds since reset: + lcd.print(millis()/1000); + } + +Note that a ``#include`` line, like :ref:`#define <lang-define>`, +has **no semicolon**. The compiler will print strange error messages +if you add one. + +C Standard Library +------------------ + +The standard C library that comes with Maple is called `newlib +<http://sourceware.org/newlib/>`_. Its main sources of documentation +are its `main reference <http://sourceware.org/newlib/libc.html>`_ +page and its `math functions +<http://sourceware.org/newlib/libm.html>`_ reference page. Here's an +example that imports the math.h library in order to take the `cube +root <http://en.wikipedia.org/wiki/Cube_root>`_ of a number:: + + #include <math.h> + + void setup() { + // no setup necessary + } + + void loop() { + // "cbrt" stands for "cube root" + double cubeRootOf3 = cbrt(3.0); + // prints a number that is approximately the cube root of 3: + SerialUSB.println(cubeRootOf3); + } + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/increment.rst b/docs/source/lang/cpp/increment.rst new file mode 100644 index 0000000..c423d1a --- /dev/null +++ b/docs/source/lang/cpp/increment.rst @@ -0,0 +1,37 @@ +.. highlight:: cpp + +.. _lang-increment: + +Increment and Decrement Operators (``++``, ``--``) +================================================== + +These operators increment (add one to) or decrement (subtract one +from) a variable. If they come before the variable, they return its +new value; otherwise, they return its old value. + +Some quick examples:: + + x++; // adds one to x, and returns the old value of x + ++x; // adds one to x, and returns the new value of x + + x--; // decrement x by one and returns the old value of x + --x; // decrement x by one and returns the new value of x + +A more extended example:: + + x = 2; + y = ++x; // x now contains 3, y contains 3 + y = x--; // x contains 2 again, y still contains 3 + +.. warning:: Be careful! You cannot put a space in between the two + ``+`` or ``-`` signs. This example is broken:: + + // this line won't compile (notice the extra space): + int y = x+ +; + +See Also +-------- + +- :ref:`lang-compoundarithmetic` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/int.rst b/docs/source/lang/cpp/int.rst new file mode 100644 index 0000000..fa63946 --- /dev/null +++ b/docs/source/lang/cpp/int.rst @@ -0,0 +1,68 @@ +.. highlight:: cpp + +.. _lang-int: + +``int`` +======= + +The ``int`` data type represents integers. Integers are your primary +data type for number storage, and store a 4 byte value. This yields a +range of -2,147,483,648 to 2,147,483,647 (minimum value of -2^31 and a +maximum value of (2^31) - 1; that's about negative 2 billion to +positive 2 billion). + +An ``int`` stores a negative number with a technique called `two's +complement math +<http://en.wikipedia.org/wiki/Two%27s_complement#Explanation>`_\ . +The highest bit in an ``int``, sometimes refered to as the "sign" bit, +flags the number as a negative number. (See the linked article on +two's complement for more information). + +The Maple takes care of dealing with negative numbers for you, so that +arithmetic operations work mostly as you'd expect. There can be an +:ref:`unexpected complication <lang-bitshift-signbit-gotcha>` in +dealing with the :ref:`bitshift right operator (>>) +<lang-bitshift>`, however. + +.. _lang-long: + +The ``long`` type is a synonym for ``int``. + +Here is an example of declaring an ``int`` variable named ``pin``, +then giving it value 13:: + + int pin = 13; + +The general syntax for declaring an ``int`` variable named ``var``, +then giving it value ``val``, looks like:: + + int var = val; + +.. _lang-int-overflow: + +Integer Overflow +---------------- + +When ``int`` variables leave the range specified above, they +:ref:`roll over <lang-variables-rollover>` in the other direction. +Here are some examples:: + + int x; + x = -2,147,483,648; + x--; // x now contains 2,147,483,647; rolled over "left to right" + + x = 2,147,483,647; + x++; // x now contains -2,147,483,648; rolled over "right to left" + +See Also +-------- + +- :ref:`unsigned int <lang-unsignedint>` +- :ref:`char <lang-char>` +- :ref:`unsigned char <lang-unsignedchar>` +- :ref:`long long <lang-longlong>` +- :ref:`unsigned long long <lang-unsignedlonglong>` +- :ref:`Integer Constants <lang-constants-integers>` +- :ref:`Variables <lang-variables>` + +.. include:: cc-attribution.txt diff --git a/docs/source/lang/cpp/intcast.rst b/docs/source/lang/cpp/intcast.rst new file mode 100644 index 0000000..da838c7 --- /dev/null +++ b/docs/source/lang/cpp/intcast.rst @@ -0,0 +1,26 @@ +.. highlight:: cpp + +.. _lang-intcast: + +``int()`` (cast) +================ + +Converts a value to the :ref:`int <lang-int>` data type. Here is +an example:: + + double d = 2.5; + int i = int(d); // i holds "2", an int value + +The value inside of the parentheses (``int(...)``) can be of any type. +However, if it is not a numeric type (like ``double``, ``char``, +etc.), you will get strange results. + +See the :ref:`int <lang-int>` reference for details about the +precision and limitations of ``int`` variables on the Maple. + +See Also +-------- + +- :ref:`int <lang-int>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/keywords.rst b/docs/source/lang/cpp/keywords.rst new file mode 100644 index 0000000..f21cd0d --- /dev/null +++ b/docs/source/lang/cpp/keywords.rst @@ -0,0 +1,204 @@ +.. _lang-keywords: + +Keywords +======== + +This page lists all of the C++ keywords, and either links to a +reference page explaining their use, or provides a brief description. + +List of Keywords +---------------- + +The C++ keywords are: + +``and``, ``and_eq``, ``asm``, ``auto``, ``bitand``, ``bitor``, +``bool``, ``break``, ``case``, ``catch``, ``char``, ``class``, +``compl``, ``const``, ``const_cast``, ``continue``, ``default``, +``delete``, ``do``, ``double``, ``dynamic_cast``, ``else``, ``enum``, +``explicit``, ``export``, ``extern``, ``false``, ``float``, ``for``, +``friend``, ``goto``, ``if``, ``inline``, ``int``, ``long``, +``mutable``, ``namespace``, ``new``, ``not``, ``not_eq``, +``operator``, ``or``, ``or_eq``, ``private``, ``protected``, +``public``, ``register``, ``reinterpret_cast``, ``return``, ``short``, +``signed``, ``sizeof``, ``static``, ``static_cast``, ``struct``, +``switch``, ``template``, ``this``, ``throw``, ``true``, ``try``, +``typedef``, ``typeid``, ``typename``, ``union``, ``unsigned``, +``using``, ``virtual``, ``void``, ``volatile``, ``wchar_t``, +``while``, ``xor``, ``xor_eq`` + +Boolean Operator Synonyms +------------------------- + +- ``and`` is a synonym for :ref:`&& <lang-boolean-and>`. +- ``not`` is a synonym for :ref:`\! <lang-boolean-not>`. +- ``not_eq`` is a synonym for :ref:`\!= <lang-comparison>`. +- ``or`` is a synonym for :ref:`|| <lang-boolean-or>`. + +Bitwise Operator Synonyms +------------------------- + +- ``and_eq`` is a synonym for :ref:`&= <lang-compoundbitwise-and>`. +- ``bitand`` is a synonym for (bitwise) :ref:`& <lang-bitwisemath-and>`. +- ``bitor`` is a synonym for :ref:`\| <lang-bitwisemath-or>`. +- ``compl`` is a synonym for :ref:`~ <lang-bitwisemath-not>`. +- ``or_eq`` is a synonym for :ref:`|= <lang-compoundbitwise-or>`. +- ``xor`` is a synonym for :ref:`^ <lang-bitwisemath-xor>`. +- ``xor_eq`` is a synonym for :ref:`^= <lang-compoundbitwise-xor>`. + +Constants +--------- + +- ``true`` and ``false`` are the :ref:`boolean constants + <lang-booleanvariables>`. + +Control Flow +------------ + +- ``break`` can exit out of a :ref:`switch statement + <lang-switchcase>` or a :ref:`for <lang-for>`, :ref:`do + <lang-dowhile>`, or :ref:`while <lang-while>` loop. + +- ``case`` defines alternatives in a :ref:`switch statement <lang-switchcase>`. + +- ``continue`` will move control flow to the next iteration of the + enclosing :ref:`for <lang-for>`, :ref:`do <lang-dowhile>`, or + :ref:`while <lang-while>` loop. + +- ``default`` defines the default alternative in a :ref:`switch + statement <lang-switchcase>`. + +- ``do`` introduces a :ref:`do <lang-dowhile>` loop. + +- ``else`` is used in :ref:`if statements <lang-if>`. + +- ``for`` introduces a :ref:`for <lang-for>` loop. + +- ``goto`` :ref:`jumps <lang-goto>` to a label. + +- ``if`` introduces an :ref:`if statement <lang-if>`. + +- ``return`` :ref:`transfers flow to a function's caller <lang-return>`. + +- ``switch`` introduces a :ref:`switch statement <lang-switchcase>`. + +- ``while`` introduces a :ref:`while <lang-while>` loop. + +Types +----- + +The following keywords are used for built-in types. + +- :ref:`bool <lang-booleanvariables>` +- :ref:`char <lang-char>` +- :ref:`double <lang-double>` +- :ref:`float <lang-float>` +- :ref:`int <lang-int>` +- :ref:`long <lang-long>` +- :ref:`short <lang-built-in-types-integral>` +- :ref:`void <lang-void>` (not really a type, but used in the absence + of one) + +The following keywords are used to introduce new types. + +- :ref:`enum <lang-enum>` + +Qualifiers +---------- + +- :ref:`static <lang-static>` can be used to declare persistent local + variables; it has other uses not documented here. + +- ``unsigned`` is used to specify an unsigned integral type. + Examples: :ref:`lang-unsignedint`, :ref:`lang-unsignedchar`. + +- :ref:`volatile <lang-volatile>` is useful when declaring variables + that may be modified by external interrupts. + +- :ref:`const <lang-const>` is used to define constants. + +Other +----- + +These keywords are not described in the Maple documentation. For more +information, consult a C++ reference. + +- ``asm`` is used to insert literal assembly language. + +- ``auto`` is used to declare that a variable has automatic storage. + +- ``catch`` is used in exception handling. Note that the default + flags we pass to :ref:`GCC <arm-gcc>` include ``-fno-exceptions``. + +- ``class`` is used to define classes. + +- ``const_cast`` is used in typecasting. + +- ``delete`` is used to free ``new``\ -allocated storage. Note that + dynamic memory allocation is not available by default on the Maple, + so you'll have to bring your own ``new`` and ``delete`` if you want + this. + +- ``dynamic_cast`` is used in typecasting. + +- ``explicit`` is used to declare constructors that can be called only + explicitly. + +- ``export`` declares a template definition accessible to other + compilation units. + +- ``extern`` can mark a declaration as a declaration and not a + definition, and also grant external linkage to a ``const`` or + ``typedef``. + +- ``friend`` is used to declare that certain functions have access to + a class's private variables. + +- ``inline`` is a compiler hint to inline a function. + +- ``mutable`` specifies that a member can be updated, even when a + member of a ``const`` object. + +- ``namespace`` declares a new namespace. + +- ``new`` dynamically allocates space for a value. Note that dynamic + memory allocation is not available by default on the Maple, so + you'll have to bring your own ``new`` and ``delete`` if you want + this. + +- ``operator`` is used to define type-specific operator overrides. + +- ``private`` declares a private class member. + +- ``protected`` declares a protected class member. + +- ``public`` declares a public class member. + +- ``register`` is a compiler hint to store a variable in a register. + +- ``reinterpret_cast`` is used in typecasting. + +- ``signed`` is the opposite of ``unsigned``. + +- ``static_cast`` is used in typecasting. + +- ``struct`` declares a new struct. + +- ``template`` introduces a template class, function, etc. + +- ``this`` is a pointer to the receiver object. + +- ``throw`` is used in exception handling. Note that the default + flags we pass to :ref:`GCC <arm-gcc>` include ``-fno-exceptions``. + +- ``try`` is used in exception handling. Note that the default + flags we pass to :ref:`GCC <arm-gcc>` include ``-fno-exceptions``. + +- ``typedef`` defines a type synonym. + +- ``union`` defines an untagged union. + +- ``using`` is a directive related to namespaces. + +- ``virtual`` declares a method which may be overridden. + +- ``wchar_t`` is the wide character type. diff --git a/docs/source/lang/cpp/longcast.rst b/docs/source/lang/cpp/longcast.rst new file mode 100644 index 0000000..493ad67 --- /dev/null +++ b/docs/source/lang/cpp/longcast.rst @@ -0,0 +1,27 @@ +.. highlight:: cpp + +.. _lang-longcast: + +``long()`` (cast) +================= + +Converts a value to the :ref:`long <lang-long>` data type. Here is +an example:: + + double d = 2.5; + long i = long(d); // i holds "2L", an long value + +The value inside of the parentheses (``long(...)``) can be of any type. +However, if it is not a numeric type (like ``double``, ``char``, +etc.), you will get strange results. + +See the :ref:`long <lang-long>` reference for details about the +precision and limitations of ``long`` variables on the Maple. + +See Also +-------- + +- :ref:`long <lang-long>` +- :ref:`long long <lang-longlong>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/longlong.rst b/docs/source/lang/cpp/longlong.rst new file mode 100644 index 0000000..d942cb4 --- /dev/null +++ b/docs/source/lang/cpp/longlong.rst @@ -0,0 +1,56 @@ +.. highlight:: cpp + +.. _lang-longlong: + +``long long`` +============= + +The ``long long`` data type stores extended size integer values. You +can use a ``long long`` when your values are too large to fit into an +:ref:`int <lang-int>`. A ``long long`` occupies 8 bytes of memory. +This yields a range of approximately -9.2×10^18 to 9.2×10^18 (that's +9.2 billion billion, or about 92 million times the number of stars in +the Milky Way galaxy). The exact range of a ``long long`` on the +Maple is from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, +or -2^63 to (2^63-1). A ``long long`` it is subject to the same +:ref:`overflow issues <lang-variables-rollover>` as any numeric data +type. + +A synonym for the ``long long`` type is ``int64``. + +Here's an example of declaring a long long (see :ref:`integer +constants <lang-constants-integers-u-l>` for an explanation of the +"LL" at the end of the number):: + + // Speed of light in nanometers per second (approximate). + long long c = 299792458000000000LL; + +The general syntax for declaring an ``long long`` variable named ``var``, +then giving it value ``val``, looks like:: + + long long var = val; + +This is identical to the ``int`` syntax, with ``long long`` (or, at +your option, ``int64``) replacing ``int``. + +Note that ``long long`` values will still :ref:`overflow +<lang-int-overflow>`, just like ``int`` values, but their much larger +range makes this less likely to happen. + +The downside to using a ``long long`` instead of an ``int`` (besides +the extra storage) is that :ref:`arithmetic <lang-arithmetic>` +operations on ``long long``\ s will take slightly longer than on +``int``\ s. + +See Also +-------- + +- :ref:`char <lang-char>` +- :ref:`unsigned char <lang-unsignedchar>` +- :ref:`int <lang-int>` +- :ref:`unsigned int <lang-unsignedint>` +- :ref:`unsigned long long <lang-unsignedlonglong>` +- :ref:`Integer Constants <lang-constants-integers>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/modulo.rst b/docs/source/lang/cpp/modulo.rst new file mode 100644 index 0000000..013d07e --- /dev/null +++ b/docs/source/lang/cpp/modulo.rst @@ -0,0 +1,70 @@ +.. highlight:: cpp + +.. _lang-modulo: + +Modulo Operator (``%``) +======================= + +Calculates the `remainder <http://en.wikipedia.org/wiki/Remainder>`_ +when one integer is divided by another. It is useful for keeping a +variable within a particular range (e.g. the size of an array). + +Syntax +------ + +:: + + dividend % divisor + +Parameters +---------- + +**dividend**: the number to be divided + +**divisor**: the number to divide by + +Returns +------- + +The remainder of **dividend**\ /\ **divisor**\ . + +Examples +-------- + +:: + + int x; + x = 7 % 5; // x now contains 2 + x = 9 % 5; // x now contains 4 + x = 5 % 5; // x now contains 0 + x = 4 % 5; // x now contains 4 + +:: + + /* update one value in an array each time through a loop */ + + int values[10]; + int i = 0; + + void setup() { + // no setup necessary + } + + void loop() { + values[i] = analogRead(0); + i = (i + 1) % 10; // modulo operator makes sure i stays between 0 and 9 + } + +Tip +--- + +The modulo operator does not work on floats. For that, you can use +the C standard library function `fmod() +<http://sourceware.org/newlib/libm.html#fmod>`_. + +See Also +-------- + +- :ref:`Arithmetic <lang-arithmetic>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/pointer.rst b/docs/source/lang/cpp/pointer.rst new file mode 100644 index 0000000..ff4ec32 --- /dev/null +++ b/docs/source/lang/cpp/pointer.rst @@ -0,0 +1,31 @@ +.. _lang-pointer: + +Pointer Operators (``&``, ``*``) +================================ + +The pointer operators ``&`` (reference) and ``*`` (dereference) are +different from the bitwise math operator :ref:`& +<lang-bitwisemath-and>` and the arithmetic operator :ref:`* +<lang-arithmetic>`. + +Pointers are one of the more complicated subjects for beginners in +learning C, and it is possible to write many useful Arduino sketches +without ever encountering pointers. However, for manipulating certain +data structures, the use of pointers can simplify the code, improve +its efficiency, and generally provide many benefits that would be +difficult to achieve without the use of pointers. + +Introducing pointers is somewhat outside the scope of this +documentation. However, a good `pointer tutorial +<http://www.cplusplus.com/doc/tutorial/pointers/>`_ is available. +Also see the `Wikipedia article on pointers +<http://en.wikipedia.org/wiki/Pointer_%28computing%29>`_, especially +the section on `pointers in C +<http://en.wikipedia.org/wiki/Pointer_%28computing%29#C_pointers>`_. + +See Also +-------- + +- http://xkcd.com/138/ + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/return.rst b/docs/source/lang/cpp/return.rst new file mode 100644 index 0000000..d9aecbe --- /dev/null +++ b/docs/source/lang/cpp/return.rst @@ -0,0 +1,60 @@ +.. highlight:: cpp + +.. _lang-return: + +``return`` +========== + +Terminates a function and return a value from a function to the +calling function, if the function has non-``void`` return type. + +Syntax: +------- + +:: + + // from within a "void" function: + return; + + // from within a non-"void" function: + return value; + +In the second case, ``value`` should have a type which is the same as +the return type of the function, or be convertible to it (like an +``int`` to a ``double``, etc.; see :ref:`this note +<lang-arithmetic-typeconversion>` for some references). + +Examples: +--------- + +A function to compare a sensor input to a threshold:: + + // converts analog readings between 0 and 400 to 0, and 400 up to 1. + int checkSensor() { + if (analogRead(0) > 400) { + return 1; + else { + return 0; + } + } + +An early ``return`` is also useful when testing a section of code +without having to "comment out" large sections of possibly buggy code, +like so:: + + void loop() { + + // brilliant code idea to test here + + return; + + // the rest of a dysfunctional sketch here + // this code will never be executed + } + +See Also +-------- + +- :ref:`comments <lang-comments>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/scope.rst b/docs/source/lang/cpp/scope.rst new file mode 100644 index 0000000..a270428 --- /dev/null +++ b/docs/source/lang/cpp/scope.rst @@ -0,0 +1,120 @@ +.. highlight:: cpp + +.. _lang-scope: + +Scope +===== + +Variables in the C++ programming language, which Maple uses (all of +your sketches are C++ programs in disguise), have a property called +*scope*. Simply put, a variable's scope is made up of all of the +lines where the variable can be used. + +Scope in C++ is a fairly complex topic, so we won't try to describe it +in full here. Instead, we present a simplified view, describing two +different kinds of scopes, *global* and *local*. For more detailed +information, consult a C++ reference. + +Global and Local Variables +-------------------------- + +A global variable is one that can be "seen" by every function in a +program. In the :ref:`Maple IDE <ide>`, any variable declared outside +of a function (like :ref:`setup() <lang-setup>` and :ref:`loop() +<lang-loop>`) is a global variable. + +A local variable can only be "seen" inside of a particular function. +You can declare a variable to be local to a function by declaring it +inside of the :ref:`curly braces <lang-curly-braces>` which enclose +that function. + +When programs start to get larger and more complex, local variables +are a useful way to ensure that a function has exclusive access to its +own variables. This prevents programming errors when one function +mistakenly modifies variables used by another function. + +It is also sometimes useful to declare and initialize a variable +inside a :ref:`for <lang-for>` loop. This creates a variable that +can only be accessed from inside the loop body. + +Example +------- + +Here is an example sketch (which you can copy into the Maple IDE and +run on your Maple) that illustrates the use of global and local +variables, as well as declaring variables inside of a ``for`` loop. +Be sure to open a :ref:`serial monitor <ide-serial-monitor>` after you +:ref:`verify <ide-verify>` and :ref:`upload <ide-upload>` the sketch:: + + int globalVar; // any function will see this variable + + void setup() { + // since "globalVar" is declared outside of any function, + // every function can "see" and use it: + globalVar = 50; + + // the variables "i" and "d" declared inside the "loop" function + // can't be seen here. see what happens when you uncomment the + // following lines, and try to Verify (compile) the sketch: + // + // i = 16; + // SerialUSB.print("i = "); + // SerialUSB.println(i); + // d = 26.5; + // SerialUSB.print("d = "); + // SerialUSB.println(d); + } + + void loop() { + // since "i" and "d" are declared inside of the "loop" function, + // they can only be seen and used from inside of it: + int i; + double d; + + for (int j = 0; j < 5; j++) { + // variable i can be used anywhere inside the "loop" function; + // variable j can only be accessed inside the for-loop brackets: + i = j * j; + SerialUSB.print("i = "); + SerialUSB.println(i); + } + + // globalVar can be accessed from anywhere. note how even + // though we set globalVar = 50 in the "setup" function, we can + // see that value here: + SerialUSB.print("globalVar = "); + SerialUSB.println(globalVar); + + // d can be accessed from anywhere inside the "loop" function: + d = 26.5; + SerialUSB.print("d = "); + SerialUSB.print(d); + SerialUSB.println(" (before separateFunction())"); + + separateFunction(); + + // notice how even though separateFunction() has a variable + // named "d", it didn't touch our (local) variable which has + // the same name: + SerialUSB.print("d = "); + SerialUSB.print(d); + SerialUSB.println(" (after separateFunction())"); + } + + void separateFunction() { + // variable "d" here has the same name as variable "d" inside of + // the "loop" function, but since they're both _local_ + // variables, they don't affect each other: + double d = 30.5; + SerialUSB.print("d = "); + SerialUSB.print(d); + SerialUSB.println(" (inside of separateFunction())"); + } + +See Also +-------- + +- `C++ programming Wikibook <http://en.wikibooks.org/wiki/C%2B%2B_Programming/Programming_Languages/C%2B%2B/Code/Statements/Scope>`_. +- Wikipedia article on `scope <http://en.wikipedia.org/wiki/Scope_%28programming%29>`_ + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/semicolon.rst b/docs/source/lang/cpp/semicolon.rst new file mode 100644 index 0000000..05e6218 --- /dev/null +++ b/docs/source/lang/cpp/semicolon.rst @@ -0,0 +1,22 @@ +.. highlight:: cpp + +.. _lang-semicolon: + +Semicolon (``;``) +================= + +Used to end a line of code. Example:: + + int a = 13; + +Tip +--- + +Forgetting to end a line in a semicolon will result in a compiler +error. The error text may be obvious, and refer to a missing +semicolon, or it may not. If an impenetrable or seemingly illogical +compiler error comes up, one of the first things to check is a +missing semicolon, in the immediate vicinity, preceding the line at +which the compiler complained. + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/sizeof.rst b/docs/source/lang/cpp/sizeof.rst new file mode 100644 index 0000000..ec2dea6 --- /dev/null +++ b/docs/source/lang/cpp/sizeof.rst @@ -0,0 +1,64 @@ +.. highlight:: cpp + +.. _lang-sizeof: + +``sizeof()`` +============ + +The ``sizeof`` operator on the Maple returns the number of bytes +needed to store a value of a given type\ [#fcharsize]_. This can be +an ordinary numeric type, like ``int``. It can be something more +complicated, like a ``struct`` or ``union``. If the argument to +``sizeof`` is an array, it returns the total number of bytes occupied +by the array. + +The general syntax looks like this:: + + sizeof(type) + sizeof(var) + +Example +------- + +The ``sizeof`` operator is useful for dealing with arrays (such as +strings) where it is convenient to be able to change the size of the +array without breaking other parts of the program. + +This program prints out a text string one character at a time. Try +changing the text phrase:: + + char myStr[] = "this is a test"; + int i; + + void setup() { + Serial.begin(9600); + } + + void loop() { + for (i = 0; i < sizeof(myStr) - 1; i++) { + Serial.print(i, DEC); + Serial.print(" = "); + Serial.println(myStr[i], BYTE); + } + } + + +Note that ``sizeof`` returns the total number of bytes. So for larger +variable types such as ``int``, the :ref:`for loop <lang-for>` +would look something like this:: + + for (i = 0; i < (sizeof(myInts)/sizeof(int)) - 1; i++) { + // do something with myInts[i] + } + +.. rubric:: Footnotes + +.. [#fcharsize] Technically (and pedantically) speaking, ``sizeof`` + returns a multiple of the number of bits a ``char`` occupies in + memory. However, on the Maple (this goes for most C++ + implementations), a ``char`` occupies 8 bits = 1 byte. All the C++ + standard guarantees, however, is that a ``char`` occupies at + *least* 8 bits. + +.. include:: /arduino-cc-attribution.txt + diff --git a/docs/source/lang/cpp/sqrt.rst b/docs/source/lang/cpp/sqrt.rst new file mode 100644 index 0000000..fbabf82 --- /dev/null +++ b/docs/source/lang/cpp/sqrt.rst @@ -0,0 +1,24 @@ +.. _lang-sqrt: + +sqrt() +====== + +Calculates the square root of a number. + +Library Documentation +--------------------- + +.. doxygenfunction:: sqrt + +Arduino Compatibility +--------------------- + +The Maple versino of ``sqrt()`` is compatible with Arduino. + +See Also +-------- + +- :ref:`pow <lang-pow>` +- :ref:`sq <lang-sq>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/static.rst b/docs/source/lang/cpp/static.rst new file mode 100644 index 0000000..8c52ba0 --- /dev/null +++ b/docs/source/lang/cpp/static.rst @@ -0,0 +1,56 @@ +.. highlight:: cpp + +.. _lang-static: + +``static`` +========== + +The ``static`` keyword can be used to create variables that are +visible to only one function. However, unlike local variables that get +created and destroyed every time a function is called, ``static`` +variables persist beyond the function call, preserving their data +between function calls. + +Variables declared as ``static`` will only be created and initialized +the first time a function is called. + +.. note:: This is only one use of the ``static`` keyword in C++. It + has some other important uses that are not documented here; consult + a reliable C++ reference for details. + +Example +------- + +One use case for ``static`` variables is implementing counters that +last longer than the functions which need them, but shouldn't be +shared to other functions. Here's an example:: + + void setup() { + SerialUSB.begin(); + } + + void loop() { + int reading; + if (timeToReadSensors()) { + reading = readSensors(); + } + // do something with reading + } + + int readSensors() { + static int numSensorReadings = 0; + numSensorReadings++; + if (numSensorReadings % 100 == 0) { + SerialUSB.print("just got to another 100 sensor readings"); + } + return analogRead(...); + } + +In this example, the static variable ``numSensorReadings`` is +initialized to zero the first time ``readSensors()`` is called, and +then incremented, so it starts out at one. Subsequent calls to +``readSensors()`` won't reset ``numSensorReadings`` to zero, because +it was declared ``static``. Thus, ``numSensorReadings`` is a count of +the number of times that ``readSensors()`` has been called. + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/string.rst b/docs/source/lang/cpp/string.rst new file mode 100644 index 0000000..3497484 --- /dev/null +++ b/docs/source/lang/cpp/string.rst @@ -0,0 +1,120 @@ +.. highlight:: cpp + +.. _lang-string: + +Strings +======= + +Text strings on the Maple can be represented with null-terminated +arrays of type :ref:`char <lang-char>`. + +Examples +-------- + +All of the following are valid declarations for strings:: + + char str1[15]; + char str2[6] = {'m', 'a', 'p', 'l', 'e'}; + char str3[6] = {'m', 'a', 'p', 'l', 'e', '\0'}; + char str4[ ] = "maple"; + char str5[6] = "maple"; + char str6[15] = "maple"; + +As you can see, there are several methods available for declaring and +initializing strings: + +- Declare an array of ``char`` without initializing it, as with ``str1``. + +- Declare an array of ``char`` (with one extra ``char``) and the + compiler will add the required null character, as with ``str2``. + +- Explicitly add the null character (``'\0'``), as with ``str3``. + +- Initialize with a string constant in quotation marks (``"..."``); + the compiler will size the array to fit the string constant and a + terminating null character (``str4``). + +- Initialize the array with an explicit size and string constant, + (``str5``). + +- Initialize the array, leaving extra space for a larger string + (``str6``). + +Null Termination +---------------- + +Generally, strings are terminated with a null character (`ASCII +<http://en.wikipedia.org/wiki/ASCII>`_ code 0). This allows functions +(like ``SerialUSB.print()``) to tell where the end of a string is. +Otherwise, they would continue reading subsequent bytes of memory that +aren't actually part of the string. + +This means that your string needs to have space for one more character +than the text you want it to contain. That is why ``str2`` and +``str5`` need to be six characters, even though "maple" is only five +-- the last position is automatically filled with a NULL +character. ``str4`` will be automatically sized to six characters, one +for the extra null. In the case of ``str3``, we've explicitly included +the null character (written ``'\0'``) ourselves. + +Note that it's possible to have a string without a final null +character (e.g. if you had specified the length of ``str2`` as five +instead of six). This will break most functions that use strings, so +you shouldn't do it intentionally. If you notice something behaving +strangely (operating on characters not in the string), however, this +could be the problem. + +Single quotes or double quotes? +------------------------------- + +Strings are always defined inside double quotes (``"Abc"``) and +characters are always defined inside single quotes (``'A'``). + +Wrapping long strings +--------------------- + +You can wrap long strings like this:: + + char myString[] = "This is the first line" + " this is the second line" + " etcetera"; + +Arrays of Strings +----------------- + +It is often convenient, when working with large amounts of text, +such as a project with an LCD display, to setup an array of +strings. Because strings themselves are arrays, this is in actually +an example of a two-dimensional array. + +In the code below, the asterisk after the datatype char ``char *`` +indicates that this is an array of "pointers". All array names are +actually pointers, so this is required to make an array of arrays. +Pointers are one of the more esoteric parts of C for beginners to +understand, but it isn't necessary to understand pointers in detail to +use them effectively here:: + + char* myStrings[] = {"This is string 1", "This is string 2", + "This is string 3", "This is string 4", + "This is string 5", "This is string 6"}; + + void setup() { + SerialUSB.begin(); + } + + void loop() { + for (int i = 0; i < 6; i++) { + SerialUSB.println(myStrings[i]); + delay(500); + } + } + + +See Also +-------- + +- :ref:`array <lang-array>` +- :ref:`__attribute__ <arm-gcc-attribute-flash>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/switchcase.rst b/docs/source/lang/cpp/switchcase.rst new file mode 100644 index 0000000..e31ccf3 --- /dev/null +++ b/docs/source/lang/cpp/switchcase.rst @@ -0,0 +1,118 @@ +.. highlight:: cpp + +.. _lang-switchcase: + +``switch``\ /\ ``case`` +======================= + +Like :ref:`if <lang-if>` statements, A ``switch`` statement controls +program flow by allowing you to specify different code that should be +executed under various cases. + +The general syntax looks like this:: + + switch (var) { + case val1: + // statements + break; + case val2: + // statements + break; + ... + default: + // statements + } + +Where ``var`` is a variable whose value to investigate, and the +``val1``, ``val2`` after each ``case`` are constant values that +``var`` might be. + +Description +----------- + +A ``switch`` statement compares the value of a variable to the values +specified in ``case`` statements. When a ``case`` statement is found +whose value matches that of the variable, the code in that case +statement is run. + +Here's a more concrete example:: + + switch (var) { + case 1: + doThing1(); + break; + case 2: + doThing2(); + break; + } + afterTheSwitch(); + +In the above example, if ``var == 1``, then the code beginning on the +line after ``case 1`` gets executed. That is, if ``var`` is one, +``doThing1()`` gets called first, and then the ``break`` statement is +executed. + +The ``break`` keyword exits the ``switch`` statement, and is typically +used at the end of each ``case``. Since there is a ``break`` at the +end of ``case 1``, the ``switch`` statement exits, and the next line +to be run is the one which calls ``afterTheSwitch()``. + +Without a ``break``, the ``switch`` statement will continue executing +the following ``case`` expressions ("falling-through") until a +``break`` (or the end of the switch statement) is reached. Let's +pretend the ``switch`` looked like this instead:: + + switch (var) { + case 1: + doThing1(); + // no break statement anymore + case 2: + doThing2(); + break; + } + afterTheSwitch(); + +Now, if ``var`` is one, ``doThing1()`` gets executed like before. +However, without a ``break``, the code would continue to be executed +line-by-line, so ``doThing2()`` would be called next. At this point, +a ``break`` has been reached, so the program continues by calling +``afterTheSwitch()``. This is usually not what you want, which is why +each ``case`` usually has a ``break`` at the end. + +.. _lang-switchcase-default: + +Writing "``default:``" instead of a ``case`` statement allows you to +specify what to do if none of the ``case`` statements matches. Having +a ``default`` is optional (you can leave it out), but if you have one, +it must appear after all of the ``case`` statements. Let's add a +``default`` to the ``switch`` we've been discussing:: + + switch (var) { + case 1: + doThing1(); + break; + case 2: + doThing2(); + break; + default: + doSomethingElse(); + } + afterTheSwitch(); + +If ``var`` is one, then ``doThing1()`` gets called. If ``var`` is +two, ``doThing2()`` gets called. If ``var`` is anything else, +``doSomethingElse()`` gets called. As stated above, a ``default`` is +optional. If you're missing one and none of the ``case`` statements +match, the ``switch`` does nothing at all, as if it weren't there. + +``switch`` statements are often used with an :ref:`enum <lang-enum>` +value as the variable to compare. In this case, you can write down +all of the values the ``enum`` takes as ``case`` statements, and be +sure you've covered all the possibilities. + +See Also: +--------- + +- :ref:`if/else <lang-if>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/unsignedchar.rst b/docs/source/lang/cpp/unsignedchar.rst new file mode 100644 index 0000000..45fedeb --- /dev/null +++ b/docs/source/lang/cpp/unsignedchar.rst @@ -0,0 +1,32 @@ +.. highlight:: cpp + +.. _lang-unsignedchar: + +``unsigned char`` +================= + +An unsigned version of the :ref:`char <lang-char>` data type. An +``unsigned char`` occupies 1 byte of memory; it stores an integer from +0 to 255. + +Like an :ref:`unsigned int <lang-unsignedint>`, an ``unsigned char`` +won't store negative numbers; it is also subject to the same +:ref:`overflow issues <lang-int-overflow>` as any integral data type. + +Example +------- + + :: + + unsigned char c = 240; + +See Also +-------- + +- :ref:`byte <lang-byte>` +- :ref:`int <lang-int>` +- :ref:`array <lang-array>` +- :ref:`SerialUSB.println() <lang-serialusb-println>` +- :ref:`Serial.println() <lang-serial-println>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/unsignedint.rst b/docs/source/lang/cpp/unsignedint.rst new file mode 100644 index 0000000..f8ea473 --- /dev/null +++ b/docs/source/lang/cpp/unsignedint.rst @@ -0,0 +1,59 @@ +.. highlight:: cpp + +.. _lang-unsignedint: + +``unsigned int`` +================ + +An ``unsigned int`` (unsigned integer) is the same as an :ref:`int +<lang-int>` in that it stores a 4 byte integer value. However, +Instead of storing both negative and positive numbers, an ``unsigned +int`` can only store nonnegative values, yielding a range of 0 to +4,294,967,295 (the positive value is 2^32 - 1). + +The difference between an ``unsigned int`` and a (signed) ``int`` lies +in the way the highest bit, sometimes referred to as the "sign" bit, +is interpreted. In the case of the Maple ``int`` type (which is +signed), if the high bit is a "1", the number is interpreted as a +negative number, using a technique known as `two's complement math +<http://en.wikipedia.org/wiki/Two%27s_complement#Explanation>`_. The +bits in an an ``unsigned int`` are interpreted according to the usual +rules for converting `binary to decimal +<http://en.wikipedia.org/wiki/Binary_numeral_system#Counting_in_binary>`_. + +An ``unsigned int`` is subject to the same :ref:`overflow issues +<lang-int-overflow>` as a regular ``int``; the only difference is +that an ``unsigned int`` will "underflow" at 0, and "overflow" at +4,294,967,295. Here is some example code which illustrates this:: + + unsigned int x; + x = 0; + x--; // x now contains 4,294,967,295; rolled over "left to right" + x++; // x now contains 0; rolled over "right to left" + +.. _lang-unsignedlong: + +The ``unsigned long`` type is a synonym for ``unsigned int``. + +Here is an example of declaring an ``unsigned int`` variable named +``pin``, then giving it value 13:: + + unsigned int pin = 13; + +The general syntax for declaring an ``unsigned int`` variable named +``var``, then giving it value ``val``, looks like:: + + unsigned int var = val; + +See Also +-------- + +- :ref:`int <lang-int>` +- :ref:`char <lang-char>` +- :ref:`unsigned char <lang-unsignedchar>` +- :ref:`long long <lang-longlong>` +- :ref:`unsigned long long <lang-unsignedlonglong>` +- :ref:`Integer Constants <lang-constants-integers>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/unsignedlonglong.rst b/docs/source/lang/cpp/unsignedlonglong.rst new file mode 100644 index 0000000..a1143f0 --- /dev/null +++ b/docs/source/lang/cpp/unsignedlonglong.rst @@ -0,0 +1,43 @@ +.. highlight:: cpp + +.. _lang-unsignedlonglong: + +``unsigned long long`` +====================== + +An unsigned version of the :ref:`long long <lang-longlong>` data type. +An ``unsigned long long`` occupies 8 bytes of memory; it stores an +integer from 0 to 2^64-1, which is approximately 1.8×10^19 (18 +quintillion, or 18 billion billion). + +A synonym for the ``unsigned long long`` type is ``uint64``. + +Like an :ref:`unsigned int <lang-unsignedint>`, an ``unsigned long +long`` won't store negative numbers; it is also subject to the same +:ref:`overflow issues <lang-int-overflow>` as any integral data type. + +Here is an example of declaring an ``unsigned long long`` variable +named ``c``, then giving it value 299,792,458,000,000,000 (see +:ref:`integer constants <lang-constants-integers-u-l>` for an +explanation of the "ULL" at the end of the number):: + + // Speed of light in nanometers per second (approximate). + unsigned long long c = 299792458000000000ULL; + +The general syntax for declaring an ``unsigned long long`` variable named +``var``, then giving it value ``val``, looks like:: + + unsigned long long var = val; + +See Also +-------- + +- :ref:`long long <lang-longlong>` +- :ref:`int <lang-int>` +- :ref:`unsigned <lang-unsignedint>` +- :ref:`char <lang-char>` +- :ref:`unsigned char <lang-unsignedchar>` +- :ref:`Integer Constants <lang-constants-integers>` +- :ref:`Variables <lang-variables>` + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/variables.rst b/docs/source/lang/cpp/variables.rst new file mode 100644 index 0000000..9ffdd1d --- /dev/null +++ b/docs/source/lang/cpp/variables.rst @@ -0,0 +1,169 @@ +.. highlight:: cpp + +.. _lang-variables: + +Variables +========= + +A variable is a way of naming and storing a value for later use by +the program, such as data from a sensor or an intermediate value +used in a calculation. + +.. contents:: Contents + :local: + +.. _lang-variables-declaring: + +Declaring Variables +------------------- + +Before they are used, all variables have to be *declared*. Declaring a +variable means defining its type, giving it a name, and (optionally) +giving it an initial value (this is often referred to as +*initializing* the variable). Variables do not have to be initialized +(given a value) when they are declared, but it is good style to give +them an initial value whenever possible. + +Here is an example of declaring a variable named ``inputVariable1`` +with type :ref:`int <lang-int>` (the ``int`` type is used to store +integers, like -2, -1, 0, 1, etc.):: + + int inputVariable1; + +In the above declaration, we did not give the variable an initial +value. Here is another example, where we declare an ``int`` variable +named ``inputVariable2``, with an initial value of ``0``:: + + int inputVariable2 = 0; + +The Maple environment comes ready to use with many useful types of +variables. See the :ref:`built-in types <lang-built-in-types>` page +for more information. + +Here are a few examples of declaring variables of different types:: + + int lightSensVal; + char currentLetter; + unsigned long long speedOfLight = 186000ULL; + char errorMessage = {"choose another option"}; // see string + +Naming Variables +---------------- + +The rules for naming a variable are simple. Names for variables can +contain letters, numbers, and underscores (the underscore is the +:kbd:`_` character), and cannot begin with a number. So +``temperature_reading``, ``tempReading``, ``tempReading1``, and +``tempReading2`` are all valid variable names, but ``4_temp_readings`` +is not, because it begins with a number. + +You cannot choose a name for a variable that is one of the C++ +:ref:`keywords <lang-keywords>`. + +Variable names are case-sensitive, so "tempreading" and "tempReading" +are different variables. However, it is very bad style to write code +that chooses variables which are the same up to case. + +You should give your variables descriptive names, so as to make your +code more readable. Variable names like ``tiltSensor`` or +``pushButton`` help you (and anyone else reading your code) understand +what the variable represents. Variable names like ``var`` or +``value``, on the other hand, do little to make your code readable. + +.. _lang-variables-scope: + +Variable Scope +-------------- + +An important choice that programmers face is where (in the program +text) to declare variables. The specific place that variables are +declared influences how various functions in a program will "see" the +variable. This is called variable *scope*. See the :ref:`scope +reference <lang-scope>` for more information. + +.. _lang-variables-initializing: + +Initializing Variables +---------------------- + +Variables may be *initialized* (assigned a starting value) when they +are declared or not. It is always good programming practice however to +double check that a variable has valid data in it before it is used. +Using a variable before you give it a value is a common source of +bugs. + +.. _lang-variables-rollover: + +Variable Rollover +----------------- + +Every (numeric) type has a valid *range*. The range of a type is the +smallest and largest value that a variable of that type can store. +For example, the :ref:`int <lang-int>` type has a range of +-2,147,483,648 to 2,147,483,647 [#frange]_. + +When variables are made to exceed their range's maximum value, they +"roll over" back to their minimum value. Note that this happens in +both directions. It's like in the game *Pac-Man* -- when Pac-Man goes +past the right edge of the screen, he reappears on the left, and when +he goes past the left side of the screen, he reappears on the right:: + + int x; + x = -2,147,483,648; + x = x - 1; // x now contains -2,147,483,647; rolled over "left to right" + + x = 2,147,483,647; + x = x + 1; // x now contains -2,147,483,648; rolled over "right to left" + +Each numeric type's reference page includes its range. See the +:ref:`built-in types <lang-built-in-types>` reference for links to each +type's reference page. + +Using Variables +--------------- + +Once variables have been declared, they are given values using the +:ref:`assignment operator <lang-assignment>`, which is a single equals +sign, ``=``. The assignment operator tells the program to store the +value on the right side of the equals sign into the variable on the +left side:: + + inputVariable1 = 7; // sets variable named inputVariable1 to 7 + inputVariable2 = analogRead(2); // sets variable named inputVariable2 to + // the (digitized) input voltage read from + // analog pin #2 + +Once a variable has been set (assigned a value), you can test its +value to see if it meets certain conditions, or you can use its value +directly. For instance, the following code tests whether the +inputVariable2 is less than 100, then sets a delay based on +inputVariable2 (which, at that point, is at least 100):: + + if (inputVariable2 < 100) { + inputVariable2 = 100; + } + + delay(inputVariable2); + +See Also +-------- + +- :ref:`lang-scope` +- :ref:`lang-built-in-types` + +.. rubric:: Footnotes + +.. [#frange] This range might seem a little weird at first. The + reasons for this range of values have to do with the fact that an + ``int`` occupies 32 bits of memory, and the facts :: + + 2^31 = -2,147,483,648 + 2^31 - 1 = 2,147,483,647 + + + Why 2^31 instead of 2^32? Well, that has to do with `how ints are + (usually) stored + <http://en.wikipedia.org/wiki/Two%27s_complement>`_ on computers. + +.. include:: /arduino-cc-attribution.txt + diff --git a/docs/source/lang/cpp/void.rst b/docs/source/lang/cpp/void.rst new file mode 100644 index 0000000..7af0acd --- /dev/null +++ b/docs/source/lang/cpp/void.rst @@ -0,0 +1,31 @@ +.. highlight:: cpp + +.. _lang-void: + +``void`` +======== + +.. cpp:type:: void + + The ``void`` keyword is used in function declarations. It indicates + that the function is expected to return no information to the + function from which it was called, or that it expects no arguments + from its caller. + +Example +------- + +:: + + // actions are performed in the functions "setup" and "loop" + // but no information is reported to the larger program + + void setup() { + // ... + } + + void loop() { + // ... + } + +.. include:: /arduino-cc-attribution.txt diff --git a/docs/source/lang/cpp/while.rst b/docs/source/lang/cpp/while.rst new file mode 100644 index 0000000..e66e0aa --- /dev/null +++ b/docs/source/lang/cpp/while.rst @@ -0,0 +1,38 @@ +.. highlight:: cpp + +.. _lang-while: + +``while`` +========= + +Syntax +------ + +:: + + while (expression) { + // block of code + } + +Description +----------- + +``while`` loops will repeat the statements inside their associated +block of code until the expression inside the parentheses becomes +:ref:`false <lang-constants-false>`. Something must change the tested +expressions' value, or the ``while`` loop will never exit. This could +be in your code, such as an incremented variable, or an external +condition, such as testing a sensor. + +Example +------- + +:: + + var = 0; + while(var < 200) { + // do something repetitive 200 times + var++; + } + +.. include:: /arduino-cc-attribution.txt |