Determine if a string is numeric: Difference between revisions

Returns true (non-zero) if character-string parameter represents a signed or unsigned integer. Otherwise returns false (zero).

''How do I determine whether a [[scalar]] is a number/whole/integer/float?''

There are also some commonly used modules for the task. [[Scalar::Util]] (distributed with 5.8) provides access to perlPerl's internal function "looks_like_number" for determining whether a variable looks like a number. Data::Types exports functions that validate data types using both the above and other regular expressions. Thirdly, there is "Regexp::Common" which has regular expressions to match various types of numbers. Those three modules are available from the CPAN.

If you're on a [[POSIX]] system, Perl supports the "[[POSIX::strtod]]" function. Its semantics are somewhat cumbersome, so here's a "getnum" wrapper function for more convenient access. This function takes a string and returns the number it found, or "[[undef]]" for input that isn't a C float. The "is_numeric" function is a front end to "getnum" if you just want to say, ''Is this a float?''

Or you could check out the String::Scanf module on the CPAN instead. The POSIX module (part of the standard Perl distribution) provides the "strtod" and "strtol" for converting strings to double and longs, respectively.