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Diffstat (limited to 'docs/source/arduino/arithmetic.rst')
| -rw-r--r-- | docs/source/arduino/arithmetic.rst | 84 |
1 files changed, 53 insertions, 31 deletions
diff --git a/docs/source/arduino/arithmetic.rst b/docs/source/arduino/arithmetic.rst index cbe3059..8fb9771 100644 --- a/docs/source/arduino/arithmetic.rst +++ b/docs/source/arduino/arithmetic.rst @@ -5,6 +5,9 @@ Addition, Subtraction, Multiplication, & Division ================================================= +.. contents:: Contents + :local: + Description ----------- @@ -17,17 +20,20 @@ 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:`arduino-int` with the value 2147483647 gives -2147483648). If the operands are of different types, the "larger" -type is used for the calculation. - -(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>`_\ -. For more information on how computers represent integers, see the -Wikipedia page on `two's complement -<http://en.wikipedia.org/wiki/Two's_complement>`_\ ). +type is used for the calculation. + +.. _arduino-arithmetic-typeconversion: + +.. 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>`_. If one of the numbers (operands) are of the type **float** or of type **double**, floating point math will be used for the @@ -55,30 +61,18 @@ Syntax result = value1 / value2; -Parameters: ------------ +Parameters +---------- **value1**: any numeric variable or constant **value2**: any numeric variable or constant +Programming Tips +---------------- -Arduino Compatibility Note --------------------------- - -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. - - -Programming Tips: ------------------ - -- Know that :ref:`integer constants <arduino-integerconstants>` - default to :ref:`int <arduino-Int>`, so some constant calculations +- Know that :ref:`integer constants <arduino-constants-integers>` + default to :ref:`int <arduino-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 @@ -93,12 +87,40 @@ Programming Tips: (the STM32 has no floating point hardware, so all floating point calculations have to be done in software). -- Use the cast operator e.g. (int)myFloat to convert one variable type +- 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): + +.. _arduino-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 -------- -- `libmaple_types.h <http://github.com/leaflabs/libmaple/blob/master/libmaple/libmaple_types.h>`_ +- The individual sizes (in bits) of various available types are + defined in `libmaple_types.h + <http://github.com/leaflabs/libmaple/blob/master/libmaple/libmaple_types.h>`_\ + . +- :ref:`sizeof <arduino-sizeof>`\ () |