number regex (incl sci notation)

jim_neophyte has asked for the wisdom of the Perl Monks concerning the following question:

Greetings, i have been looking for a better way to write a regex for determining if a string is a number, including integers, floating pt numbers, and scientific notation. seems so obfuscated that it has to be wrong. please point out errors, omissions, etc. so far, i have looked at cpan and the perlmonks archive. i have only found regexs for more well-behaved strings. the output i need to parse includes (some of these are ill-formed, but "it's a liven'!":

1.0
-1.0
.9
9.
-.9
-.4e08
+4.E-08
+.2e+219
2.00001e+9
[download]

the code that i have and not sure about is:

our $numregex = qr/^
        # may have leading plus or minus
        [-+]?
        # one of these formats must exist
        (?:
          # maybe one or more digits, then decimal, and maybe more dig
+its
          \d+\.?\d*
          # or decimal followed by one or more digits
          |\.\d+
        )
        # optional sci notation
        (?:
          # "e" or "E" and plus or minus, and one, two, or three digit
+s
          [eE][-+]\d{1,3}
        )?
        $/x;
[download]

thank you.

Comment on number regex (incl sci notation) Select or Download Code

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Re: number regex (incl sci notation) by VSarkiss (Monsignor) on Dec 07, 2004 at 19:21 UTC
This is a faq. Try some of the other possibilities listed from `perldoc -q number`. My personal recommendation is to use Scalar::Util. It includes a routine `looks_like_number` that will handle anything that Perl thinks is a number. Do not rebuke them with harsh words ... but rather lead them gently - with URLs - so that they may learn wisdom.	[reply] [d/l] [select]
Re^2: number regex (incl sci notation) by jim_neophyte (Sexton) on Dec 07, 2004 at 20:16 UTC
thanks for the assist. i had forgotten about the "perldoc -q" thing. also, the Scalar::Util qw( looks_like_number ) works wonderfully in my quick testing. thanks again.	[reply]
Re^2: number regex (incl sci notation) by rrwo (Friar) on Dec 07, 2004 at 20:21 UTC
Scalar::Util's looks_line_number() routine checks the Perl API Looks Like Number field in the scalar. In some cases your variable might have a string which is a valid number, but doesn't have that field set.	[reply]
Re^3: number regex (incl sci notation) ("looks" not has IV) by tye (Sage) on Dec 08, 2004 at 06:24 UTC
There is no "looks like a number field" in a scalar. looks_like_number() checks whether a string looks like a number. This is independent of whether the scalar has an IV stored in it (which appears to be what you are thinking of). - tye	[reply]
Re: number regex (incl sci notation) by Anonymous Monk on Dec 07, 2004 at 23:57 UTC
Use Regexp::Common::number.	[reply]