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How do I determine whether a scalar is a number/wh

Jasmine
Administrator

Jan 19, 2001, 3:39 PM

Post #1 of 1 (1985 views)

How do I determine whether a scalar is a number/wh	Can't Post

(From the Perl FAQ)

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

Assuming that you don't care about IEEE notations like ``NaN'' or ``Infinity'', you probably just want to use a regular expression.

Code

   warn "has nondigits"        if     /\D/; 
   warn "not a natural number" unless /^\d+$/;             # rejects -3 
   warn "not an integer"       unless /^-?\d+$/;           # rejects +3 
   warn "not an integer"       unless /^[+-]?\d+$/; 
   warn "not a decimal number" unless /^-?\d+\.?\d*$/;  # rejects .2 
   warn "not a decimal number" unless /^-?(?:\d+(?:\.\d*)?|\.\d+)$/; 
   warn "not a C float" 
       unless /^([+-]?)(?=\d|\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/;

If you're on a POSIX system, Perl's 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 http:// instead. The POSIX module (part of the standard Perl distribution) provides the strtol and strtod for converting strings to double and longs, respectively.

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