SPUG: hashes, arrays, map, join
Colin Meyer
cmeyer at helvella.org
Fri Mar 9 19:38:17 CST 2001
On Fri, Mar 09, 2001 at 04:53:06PM -0800, John Cokos, CEO, iWeb, Inc. wrote:
> 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);
>
How about:
$r = join ',', map "$_:$ids{$_}", keys %ids;
-C.
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