math
----

Mathematical expressions.

::

  math(EXPR <output-variable> <math-expression>)

``EXPR`` evaluates mathematical expression and returns result in the
output variable.  Example mathematical expression is ``5 * (10 + 13)``.
Supported operators are ``+``, ``-``, ``*``, ``/``, ``%``, ``|``, ``&``,
``^``, ``~``, ``<<``, ``>>``, and ``(...)``.  They have the same meaning
as they do in C code.
