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Re: Re: Checking whether a $var is a number

by wog (Curate)
on Sep 05, 2001 at 00:32 UTC ( [id://110151]=note: print w/replies, xml ) Need Help??


in reply to Re: Checking whether a $var is a number
in thread Checking whether a $var is a number

Unfortunatly checking for non-digits is not sufficient since these are all numbers:

  • 12.7
  • 1E0
  • 1.477e7

Checking just for non-digits won't work on those. And you cannot just check for digits, E, e, and ., since these are all not numbers

  • ...
  • Eeeeeee.
  • 12e
  • e15
  • 1.6.8

The only thing that your technique will work for is integers -- certainly not the only thing meant by 'number'.

  • Comment on Re: Re: Checking whether a $var is a number

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Re: Re: Re: Checking whether a $var is a number
by Ted Nitz (Chaplain) on Sep 05, 2001 at 01:01 UTC
    that's easy to fix (untested):
    qr/(?:+|-)?\d+(?:\.)?(?:\d+)?(?:[Ee](?:+|-)?\d+)/

    piece by piece:
    (?:+|-)?            # Optional leading + or -
\d+                 # One or more digit
(?:\.)?             # A trailing . 12. is a number I think
(?:\d+)?            # The part after the decimal
(?:[Ee](?:+|-)?\d+) # E or e followed by an optional + or - and one or
+ more digit

    [download]
    I don't think I left anything out. Now, this won't match .4 as a number.... You can build a regex that will handle that case properly as well. But the simple fix of making the part before the decimal optional causes another bug, it maks every part optional, so the null string would be a match, and since every string starts with a null string, every string would match. Since all we have is a number, we could anchor to the begenning and end of the value, but then, the empty string would still match. Thinking back to his origonial question, this should be anchored to the front and back, so more like qr/^...$/.
    -Ted
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