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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-compoundbitwise>` (``&=``,
``|=``, ``^=``).
- :ref:`if statement <lang-if>`
.. include:: cc-attribution.txt
|
