Function: string-to-number

Parse STRING as a decimal number and return the number.
This parses both integers and floating point numbers.
It ignores leading spaces and tabs, and all trailing chars.

If BASE, interpret STRING as a number in that base. If BASE isn't
present, base 10 is used. BASE must be between 2 and 16 (inclusive).
If the base used is not 10, STRING is always parsed as integer.
(fn STRING &optional BASE)