SWI-Prolog -- number

Availability:built-in

number_string(?Number, ?String)

Bi-directional conversion between a number and a string. At least one of the two arguments must be instantiated. Besides the type used to represent the text, this predicate differs in several ways from its ISO cousin:^{143Note that SWI-Prolog's
syntax for numbers is not ISO compatible either.}

If String does not represent a number, the predicate fails rather than throwing a syntax error exception.
Leading white space and Prolog comments are not allowed.
Numbers may start with '+' or '-'.
It is not allowed to have white space between a leading '+' or '-' and the number.
Floating point numbers in exponential notation do not require a dot before exponent, i.e., "1e10" is a valid number.