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.. highlight:: cpp
.. _lang-random:
random()
========
The ``random()`` function generates pseudo-random numbers.
Library Documentation
---------------------
.. FIXME [Breathe] use doxygenfunction when possible
.. cpp:function:: random(long max)
Same as a call to ``random(0, max)``.
.. cpp:function:: random(long min, long max)
Generate a pseudo-random number with given lower and upper bounds.
*Parameters*
- ``min`` - Lower bound on the returned value, inclusive
- ``max`` - Upper bound on the returned value, exclusive
*Returns*: A pseudo-random number in the range [min, max).
Discussion
----------
If it is important for a sequence of values generated by
:ref:`random() <lang-random>` to differ, on subsequent executions of a
sketch, use :ref:`randomSeed() <lang-randomseed>` to initialize the
random number generator with a fairly random input, such as
:ref:`analogRead() <lang-analogread>` on an unconnected pin.
Conversely, it can occasionally be useful to use pseudorandom
sequences that repeat exactly. This can be accomplished by calling
``randomSeed()`` with a fixed number, before starting the random
sequence.
Example
-------
The following sketch initializes the random seed based on an :ref:`ADC
<adc>` reading of pin 0. If this pin is unconnected, the Sketch
should print different values to the :ref:`serial monitor
<ide-serial-monitor>` each time it is run::
long randNumber;
void setup() {
pinMode(0, INPUT_ANALOG);
randomSeed(analogRead(0));
}
void loop() {
randNumber = random(300);
SerialUSB.println(randNumber);
delay(50);
}
See Also
--------
- :ref:`randomSeed() <lang-randomseed>`
.. include:: /arduino-cc-attribution.txt
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