SPUG: hashes, arrays, map, join

John Cokos, CEO, iWeb, Inc. jcokos at iwebsys.com
Fri Mar 9 18:53:06 CST 2001

I've been knocking my head agains the wall all day 
on this stupid little problem ... somebody please
bail me out.

Assume a string like this.
   my $results = "12345:15,32984732:25,733263:12,349874:5";

I want to place it into a hash, keyed by the first number,
valued by the second one.  That's not a problem.
   my %ids = ();
   %ids = map { split(/\:/) } split(/\,/,$results);

Now, I need to add (or delete) some of these keys.
   delete $ids{12345};
   $ids{5555} = 12;

Again, no problem, that works.

The pickle, is getting this updated hash back into the comma
separated format that it started with.  Totally lost here.

This just flattens it.
         print join(",", %ids);

This works, but it's hideous (gotta be a smoother way).  I can
see this being a pretty intense maneuver on a large set:
          my %set = ();
          my @array;
          foreach my $key ( keys %ids) { push @array, "$key:$ids{$key}"; }
          print join(",", @array);

Note, that in real life, that string ($results, above) may have upwards
of 100,000 comma separated values, so something efficient is pretty

Appreciate your advice, everyone.


  John Cokos, President / CEO: iWeb Inc.
  jcokos at ccs.net

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