Louis Pouzin wrote:
>
> That's slick. I like it. I feel getting better at climbing down hash trees.
> One thing hangs me up. What's "{$s}++" doing at the end of:
> $h{${$lis{$i}{$j}}[1]}{${$lis{$i}{$j}}[0]}{$s}++;
>
> {$s} looks like one hash deeper with key $s, sorted at the end of your script.
> But then ++. Watsit ?
> Another Perl trick I've got to learn ?
>
> Thanks a lot.
you know that $x++ postincrements $x? well, using it in things like
$h{$x}++;#A
you increment the key's related value, like
$h{$x}=$h{$x}+1;
So, using #A rather than
$h{$x}=1;#B
means that if any key occurs more than once, you get its frequency.
$h{cat}=$h{cat}+1;
$h{cat}=$h{cat}+1;
$h{cat}=$h{cat}+1;
print "$h{cat} cats\n";
$h{dog}++;
$h{dog}++;
$h{dog}++;
print "$h{dog} dogs\n";
> - -
> On Tue, 21 Jan 2003 16:39:39 -0800, Richard Cook wrote:
>
> >#!/usr/bin/perl -w
> >BEGIN { $^W = 1 }
> >use strict;
> >my %lis; #age sex
> >$lis{cat}{Zoe}=["9","female"];
> >$lis{dog}{Max}=["8","male"];
> >$lis{pig}{Joe}=["6","barrow"];
> >$lis{cat}{Sam}=["1","female"];
> >$lis{dog}{Bob}=["2","male"];
> >$lis{cat}{Kat}=["5","female"];
> >$lis{pig}{Sly}=["7","barrow"];
> >$lis{cat}{Tom}=["1","male"];
> >$lis{pig}{Zig}=["3","barrow"];
>
> >print "-"x32,"\n";
> >my %h;
> >for my $i (keys %lis){
> > for my $j (keys %{$lis{$i}}){
> > my $s = ", a pet $i named $j; ";
> > $h{${$lis{$i}{$j}}[1]}{${$lis{$i}{$j}}[0]}{$s}++;
> > } #sex age
> >}
> >for my $h (sort { $a cmp $b } keys %h){
> > print "sex $h: ";
> > for my $i (sort {$a <=> $b} keys %{$h{$h}}){
> > print "age $i";
> > for my $s (sort keys %{$h{$h}{$i}}){
> > print "$s";
> > }
> > }
> > print "\n";
> >}
> >#END
