Beefy Boxes and Bandwidth Generously Provided by pair Networks
Pathologically Eclectic Rubbish Lister
 
PerlMonks  

Re: Re: Luhn Number Golf

by PrakashK (Pilgrim)
on Feb 26, 2002 at 21:47 UTC ( #147740=note: print w/ replies, xml ) Need Help??


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

++. You can eliminate reverse and shorten it to 55.

sub luhn { # 1 2 3 4 5 #234567890123456789012345678901234567890123456789012345 my$s;$_=pop;~s/(.)(.)/$2.$1*2/ge;$s+=$_ for/./g;!chop$s }
and, if you don't care for strict-ness, shave another 5 chars, by eliminating my$s;

/prakash


Comment on Re: Re: Luhn Number Golf
Select or Download Code
Re: Re: Re: Luhn Number Golf
by chipmunk (Parson) on Feb 26, 2002 at 22:15 UTC
    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.

      If you aren't going for strictness, you can get the same initialization effect with
      ($_,$s)=@_
      Which is one char shorter than
      my$s;$_=pop
      If you also want to keep strictness, you can always sidestep it by replacing $s with a global punctuation variable.

      -Blake

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://147740]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others browsing the Monastery: (7)
As of 2015-07-05 18:05 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (67 votes), past polls