Re^2: Simple formatting question for credit card number

Careful. Context will trip you up when playing with reverse. ++ otherwise.

return scalar reverse $num;
[download]

Why does everyone reach for substitution though?

sub format_cc_num {
    my ($num, $spacer) = @_;
    scalar reverse join $spacer, (reverse $num) =~ /(....)/g;
}
[download]

Makeshifts last the longest.

Comment on Re^2: Simple formatting question for credit card number Select or Download Code

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Re3: Simple formatting question for credit card number by dragonchild (Archbishop) on Aug 13, 2003 at 13:00 UTC
Actually, we both were buggy. Using your code and my code (with the appropriate bugfix), we have: `#!/usr/bin/perl use strict; use warnings; my $x = "12345678"; my $y = "123456789"; sub dragonchild { my ($n, $s) = @_; $n = reverse $n; # Added negative lookahead $n =~ s/(.{4})(?!$)/${1}${s}/g; scalar reverse $n; } sub aristotle { my ($n, $s) = @_; scalar reverse join $s, (reverse $n) =~ /(....)/g; } foreach my $v ($x, $y) { print dragonchild($v, '-'), $/; print aristotle($v, '-'), $/; } ------ 1234-5678 1234-5678 1-2345-6789 2345-6789` [download] Your code only works for card numbers that are a multiple of 4. Most department store cards are 11 digits and some, like AmEx, are moving to 17 or 19 digits. (I used to work for MC ... we had a similar function that I had to maintain in the app I worked on. It was written horribly with substr and the like.) ------ We are the carpenters and bricklayers of the Information Age. The idea is a little like C++ templates, except not quite so brain-meltingly complicated. -- TheDamian, Exegesis 6 Please remember that I'm crufty and crochety. All opinions are purely mine and all code is untested, unless otherwise specified.	[reply] [d/l]
Re^3: Simple formatting question for credit card number by Aristotle (Chancellor) on Aug 13, 2003 at 14:28 UTC
Oops. I was going to use unpack at first and didn't think about that when going for the pattern instead. The fix is obvious, though. `sub format_cc { my ($n, $s) = @_; scalar reverse join $s, (reverse $n) =~ /(.{1,4})/g; }` [download] Makeshifts last the longest.	[reply] [d/l]