``math`` is used to perform mathematical calculations. It supports all the usual operations such as addition, subtraction, etc. As well as functions like ``abs()``, ``sqrt()`` and ``log2()``.
By default, the output is as a float with trailing zeroes trimmed. To get a fixed representation, the ``--scale`` option can be used, including ``--scale=0`` for integer output.
Keep in mind that parameter expansion takes before expressions are evaluated. This can be very useful in order to perform calculations involving shell variables or the output of command substitutions, but it also means that parenthesis (``()``) and the asterisk (``*``) glob character have to be escaped or quoted.
``math`` ignores whitespace between arguments and takes its input as multiple arguments (internally joined with a space), so ``math 2 +2`` and ``math "2 + 2"`` work the same. ``math 2 2`` is an error.
-``-sN`` or ``--scale=N`` sets the scale of the result. ``N`` must be an integer or the word "max" for the maximum scale. A scale of zero causes results to be rounded down to the nearest integer. So ``3/2`` returns ``1`` rather than ``2`` which ``1.5`` would normally round to. This is for compatibility with ``bc`` which was the basis for this command prior to fish 3.0.0. Scale values greater than zero causes the result to be rounded using the usual rules to the specified number of decimal places.
Fish 1.x and 2.x releases relied on the ``bc`` command for handling ``math`` expressions. Starting with fish 3.0.0 fish uses the tinyexpr library and evaluates the expression without the involvement of any external commands.
You don't need to use ``--`` before the expression even if it begins with a minus sign which might otherwise be interpreted as an invalid option. If you do insert ``--`` before the expression it will cause option scanning to stop just like for every other command and it won't be part of the expression.
