From d9cbd78e29d42e70bb46641dd43ee0772c8c975f 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.

---
 source/lang/boolean.rst | 91 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 91 insertions(+)
 create mode 100644 source/lang/boolean.rst

(limited to 'source/lang/boolean.rst')

diff --git a/source/lang/boolean.rst b/source/lang/boolean.rst
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+.. 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-bitwisecompound>` (``&=``,
+  ``|=``, ``^=``).
+- :ref:`if statement <lang-if>`
+
+
+.. include:: cc-attribution.txt
-- 
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