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Re: Re: Re: Luhn Number Golf

by chipmunk (Parson)
on Feb 26, 2002 at 22:15 UTC ( #147748=note: print w/ replies, xml ) Need Help??

in reply to Re: Re: Luhn Number Golf
in thread Luhn Number Golf

Unfortunately, you can't simply eliminate reverse. Cody Pendant explained why in the comments in his solution; if the number has an odd number of digits, you'll end doubling the wrong digits. For example, your solution would return true for 548979844, which is not a Luhn number.

You shouldn't eliminate my$s; either. That's not there for strict-ness, but to allow the subroutine to be called more than once. Without it, $s would keep its values between calls, throwing off all the subsequent answers.

Comment on Re: Re: Re: Luhn Number Golf
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Re: Re: Re: Re: Luhn Number Golf
by blakem (Monsignor) on Mar 08, 2002 at 09:10 UTC
    If you aren't going for strictness, you can get the same initialization effect with
    Which is one char shorter than
    If you also want to keep strictness, you can always sidestep it by replacing $s with a global punctuation variable.


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