arduino language reference nearing completion, properly CC-BY-SA 3.0 attributed

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+.. highlight:: cpp
+
+.. _arduino-arithmeticcompound:
+
+Compound Arithmetic Operators (``+=`` , ``-=``, ``*=``, ``/=``)
+===============================================================
+
+Description
+-----------
+
+Perform a mathematical operation on a variable with another constant
+or variable.  These operators are just a convenient shorthand::
+
+    x += y;   // equivalent to the expression x = x + y;
+    x -= y;   // equivalent to the expression x = x - y;
+    x *= y;   // equivalent to the expression x = x * y;
+    x /= y;   // equivalent to the expression x = x / y;
+
+Here is an example::
+
+    int x = 2;
+    int y = 10;
+
+    x += 4;          // x now contains 6
+    x -= 3;          // x now contains 3
+    x *= y;          // x now contains 30
+    x /= 2;          // x now contains 15
+    x += max(20, 6); // x now contains 35
+    x -= sq(5);      // x now contains 15
+
+Parameters
+----------
+
+**x**: a numeric variable
+
+**y**: a numeric variable, number constant, or any other expression
+that evaluates to a number (e.g. call to a function that returns a
+number).
+
+See Also
+--------
+
+- :ref:`Arithmetic operators <arduino-arithmetic>`