From 5e587be27a7c3bd854b686952a5c9637a2432ff0 Mon Sep 17 00:00:00 2001
From: Marti Bolivar <mbolivar@mit.edu>
Date: Sun, 28 Nov 2010 11:23:33 -0500
Subject: reorganized all the arduino/ docs into a lang/ subdirectory since
 they're properly CC attributed now.

---
 docs/source/lang/arithmetic.rst | 129 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 129 insertions(+)
 create mode 100644 docs/source/lang/arithmetic.rst

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diff --git a/docs/source/lang/arithmetic.rst b/docs/source/lang/arithmetic.rst
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+.. highlight:: cpp
+
+.. _lang-arithmetic:
+
+Addition, Subtraction, Multiplication, & Division
+=================================================
+
+.. contents:: Contents
+   :local:
+
+Description
+-----------
+
+These operators return 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 2147483647 gives
+-2147483648). If the operands are of different types, the "larger"
+type is used for the calculation.
+
+.. _lang-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
+calculation.
+
+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
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