Question

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How do I tell if a variable has a numeric value in Perl?

I want to decide if a variable (value parsed from a string) is a number or not. How can I do that? Well, I guess /^[0-9]+$/ would work, but is there a more elegant version?

Answer 1

if (/\D/)            { print "has nondigits\n" }
if (/^\d+$/)         { print "is a whole number\n" }
if (/^-?\d+$/)       { print "is an integer\n" }
if (/^[+-]?\d+$/)    { print "is a +/- integer\n" }
if (/^-?\d+\.?\d*$/) { print "is a real number\n" }
if (/^-?(?:\d+(?:\.\d*)?&\.\d+)$/) { print "is a decimal number\n" }
if (/^([+-]?)(?=\d&\.\d)\d*(\.\d*)?([Ee]([+-]?\d+))?$/)
                     { print "a C float\n" }

taken from here: http://rosettacode.org/wiki/Determine_if_a_string_is_numeric#Perl