It has been a while since there has been a good round of golf, so I decided to post one. I couldn't come up with a nice interesting math brain-teaser, so I'll post this one.

The Rules
Expected Input-Output
My Swing (83 chars) 
sub a
{
$_=pop;($_=reverse sprintf"%.2f",$_)=~s/(\d\d\d(?=\d))/$1,/g,return re
+verse split''
}

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Enoch

(update: Changed "integer" to "number". Integers don't have decimals. Thanks to xylus for pointing out my err.

Replies are listed 'Best First'.
Re: (Golf) Formatting Integer To Money
by Abigail-II (Bishop) on Aug 29, 2002 at 17:04 UTC
    57 characters: 
    sub a{$_=sprintf"%.2f",pop;{s/(\d)(\d{3})(?!\d)/$1,$2/&&redo}$_}

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    Abigail
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      49 Characters: 
      sub a{$_=sprintf"%.2f",pop;while(s/\B\d{3}\b/,$&/){}$_}

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      Update: 48 characters: 
      sub a{$_=sprintf"%.2f",pop;{s/\B\d{3}\b/,$&/&&redo}$_}

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      --Dave
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        Here's a 44 with a few small improvements to yours: 
        sub a{$_=sprintf"%.2f",@_;1while s/\B...\D/,$&/;$_}

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        It seems that the sprintf solutions fail sometimes in rounding, e.g. "123456789012345.125" becomes "123,456,789,012,345.12" instead of "123,456,789,012,345.13".

        Update: I was just informed by thospel++ that IEEE rounding is toward even, not upward. That explains the behavior, though I'm not sure if it's the desired behavior for this problem.

        -- Mike

        --
        just,my${.02}

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      Why the need for sprintf ?? Am I missing something of importance?

      If sprintf is not needed, here is one at 49 chars.... 
      sub a{$_=pop;{s/(\d)(\d{3})(?!\d)/$1,$2/&&redo}$_.'.00'}

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      update: I am a little confused about the input, the post asks for an integer, which would not have any decimal places, but some of the input has a decimal place..
      Should this handle input with decimal places, or should it just trust that the user submits integers only? 
      perl -e '$_=$0;split??;chop$_;$;=pop@_;$;++for(0..9060420);$_.=reverse
+$;;print'

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        To get the precision correct. Your script fails if you input 1234.56.

        ++Abigail-II

        enoch
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Re: (Golf) Formatting NumberTo Money
by Anonymous Monk on Aug 29, 2002 at 18:36 UTC 
    # 48

sub f { use Number::Format':subs';format_number(pop,2,2) }
        #23456789012345678901234567890123456789012345678

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Re: (Golf) Formatting Integer To Money
by Aristotle (Chancellor) on Aug 29, 2002 at 17:53 UTC
    53 
    #        1         2         3         4         5
#2345678901234567890123456789012345678901234567890123
$_=sprintf"%.2f",pop;{s/(^\d+)(\d{3})/$1,$2/&&redo}$_

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    Makeshifts last the longest.

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Re: (Golf) Formatting NumberTo Money
by Django (Pilgrim) on Aug 29, 2002 at 19:06 UTC
    54 without declaration, else 61
    sub a{$_=sprintf"%.2f",pop;{s/(\d+)(\d{3}.*)/$1,$2/?redo:$_}}

    ~Django

    "Why don't we ever challenge the spherical earth theory?"

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