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+.. highlight:: cpp
+
+.. _lang-constrain:
+
+constrain()
+===========
+
+(Macro) Constrains a number to be within a range.
+
+Syntax
+------
+
+::
+
+    constrain(x, a, b)
+
+
+Parameters
+----------
+
+**x**: the number to constrain
+
+**a**: the lower end of the range
+
+**b**: the upper end of the range
+
+Returns
+-------
+
+**x**: if **x** is between **a** and **b**
+
+**a**: if **x** is less than **a**
+
+**b**: if **x** is greater than **b**
+
+Example
+-------
+
+::
+
+    // limits range of sensor values to between 10 and 150:
+    sensVal = constrain(sensVal, 10, 150);
+
+
+Warning
+-------
+
+Because of the way ``constrain()`` is implemented, avoid using other
+functions or causing side effects inside the parentheses, as it may
+lead to incorrect results::
+
+    constrain(x,a++,b);   // avoid this - yields incorrect results
+
+    constrain(x,a,b);     // use this instead-
+    a++;                  // keep other math outside constrain()
+
+Arduino Compatibility
+---------------------
+
+Maple's implementation of ``constrain()`` is compatible with Arduino.
+
+See Also
+--------
+
+-  :ref:`min() <lang-min>`
+-  :ref:`max() <lang-max>`
+
+.. include:: /arduino-cc-attribution.txt