aboutsummaryrefslogtreecommitdiffstats
path: root/docs/source/lang/cpp/arithmetic.rst
diff options
context:
space:
mode:
authorMarti Bolivar <mbolivar@mit.edu>2010-12-21 10:27:37 -0500
committerMarti Bolivar <mbolivar@mit.edu>2010-12-21 10:27:37 -0500
commitc45bccad44187da27505cf5808424e709e3f54a1 (patch)
tree18a459a50f8d0551ba046e30462c93999d982725 /docs/source/lang/cpp/arithmetic.rst
parent84fd2532a7f23d20354ff590790b3f892cb7e7d7 (diff)
parentd5ad2a27f4e69e6cc9324331945937c983c30366 (diff)
downloadlibrambutan-c45bccad44187da27505cf5808424e709e3f54a1.tar.gz
librambutan-c45bccad44187da27505cf5808424e709e3f54a1.zip
Merge branch 'master' into debug-serialusb.
Chose debug-serialusb version in cases of conflict. Conflicts: libmaple/usb/usb_callbacks.c
Diffstat (limited to 'docs/source/lang/cpp/arithmetic.rst')
-rw-r--r--docs/source/lang/cpp/arithmetic.rst127
1 files changed, 127 insertions, 0 deletions
diff --git a/docs/source/lang/cpp/arithmetic.rst b/docs/source/lang/cpp/arithmetic.rst
new file mode 100644
index 0000000..91fe22e
--- /dev/null
+++ b/docs/source/lang/cpp/arithmetic.rst
@@ -0,0 +1,127 @@
+.. 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 `libmaple_types.h
+ <http://github.com/leaflabs/libmaple/blob/master/libmaple/libmaple_types.h>`_\
+ .
+
+- :ref:`sizeof <lang-sizeof>`\ ()
+
+
+.. include:: cc-attribution.txt