Subj : Re: any function to handle this kind of counting?
To   : comp.programming
From : Rob Thorpe
Date : Thu Aug 04 2005 03:44 am

John W. Krahn wrote:
> Rob Thorpe wrote:
> > Peter Ammon wrote:
> >>Just wait 'til the Perl guy gets here, though!
> >
> > I can take on that mantle:
> >
> > for(0..($#a<$#b?$#a:$#b)){++$ans{$b[$_]}{$a[$_]};}
>
> Way too much punctuation and not enough whitespace.  :-)
>
> ++$ans{ $b[ $_ ], $a[ $_ ] } for 0 .. ( @a < @b ? $#a : $#b );

I know, I was being facetious :)

> You don't really need a hash of hashes as perl will concatenate comma
> separated values in the hash key.
>
> $ perl -e'
> @a = qw/ a b a e a /;
> @b = qw/ 1 2 1 4 5 /;
> $; = "";  # change the subscript separator
> ++$ans{ $b[ $_ ], $a[ $_ ] } for 0 .. ( @a < @b ? $#a : $#b );
> print "$_\t$ans{$_}\n" for sort keys %ans;
> '
> 1a	2
> 2b	1
> 4e	1
> 5a	1

I was making a data-structure the same as Jon's hash-of-hashes.  The
data structure you mention could be used.  But if it was then AFAIK
using "keys" to go through it later might not be so easy.

.