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diff --git a/source/arduino/boolean.rst b/source/arduino/boolean.rst index f109bdb..a724c20 100644 --- a/source/arduino/boolean.rst +++ b/source/arduino/boolean.rst @@ -1,94 +1,86 @@ +.. highlight:: cpp + .. _arduino-boolean: Boolean Operators ================= -These can be used inside the condition of an -`if <http://arduino.cc/en/Reference/If>`_ statement. +These can be used inside the condition of an :ref:`if <arduino-if>` +statement. +.. contents:: Contents + :local: +.. _arduino-boolean-and: && (logical and) -~~~~~~~~~~~~~~~~ - -True only if both operands are true, e.g. +---------------- -:: +True only if both operands are true. For example:: - if (digitalRead(2) == HIGH && digitalRead(3) == HIGH) { // read two switches + if (digitalRead(2) == HIGH && digitalRead(3) == HIGH) { // read two switches // ... - } + } + +is true only if both inputs are high. Another example:: -is true only if both inputs are high. + 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 ``&&``. -\|\| (logical or) -~~~~~~~~~~~~~~~~~ +.. _arduino-boolean-or: -True if either operand is true, e.g. +\|\| (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. +is true if either ``x`` or ``y`` is greater than 0. +! (logical not) +--------------- -! (not) -~~~~~~~ +True if the operand is false. For example:: -True if the operand is false, e.g. - -:: - - if (!x) { + if (!x) { // ... - } - -is true if x is false (i.e. if x equals 0). - - - -Warning -------- + } -Make sure you don't mistake the boolean AND operator, && (double -ampersand) for the bitwise AND operator & (single ampersand). They -are entirely different beasts. +is true if ``x`` is false (i.e. if ``x`` equals zero). +Some Advice +----------- +.. warning:: -Similarly, do not confuse the boolean \|\| (double pipe) operator -with the bitwise OR operator \| (single pipe). + Make sure you don't mistake the boolean AND operator ``&&`` + (double ampersand) for the :ref:`bitwise AND operator + <arduino-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 <arduino-bitwisemath-or>` + ``|`` (single pipe). + The :ref:`bitwise NOT operator <arduino-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. -The bitwise not ~ (tilde) looks much different than the boolean not -! (exclamation point or "bang" as the programmers say) but you -still have to be sure which one you want where. - - -Examples --------- - -:: - - if (a >= 10 && a <= 20){} // true if a is between 10 and 20 - - - -See also +See Also -------- - -- `& <http://arduino.cc/en/Reference/BitwiseAnd>`_ (bitwise AND) -- `\| <http://arduino.cc/en/Reference/BitwiseAnd>`_ (bitwise OR) -- `~ <http://arduino.cc/en/Reference/BitwiseXorNot>`_ (bitwise NOT -- `if <http://arduino.cc/en/Reference/If>`_ - - +- :ref:`Bitwise operators <arduino-bitwisemath>` (``&``, ``|``, ``^``, ``~``) +- :ref:`Compound bitwise operators <arduino-bitwisecompound>` (``&=``, + ``|=``, ``^=``). +- :ref:`if statement <arduino-if>` |