Re: creating defined references to arrays of size zero

Like Ovid said:

my %stacks = ( A => [],
               B => [],
                  .
                  .
                  .
               Z => [],
             );

# microseconds later...

my $current_stack = $stacks{ K };  # for example

push @$current_stack, 'whatever';

# etc.;
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As long as you deal with references (like $current_stack) above, the changes you make will be reflected in the stacks stored in %stacks.

You can initialize the stacks more succinctly with something like this:

my %stacks; @stacks{ @names } = map [], @names;
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...where @names holds the names of the stacks.

the lowliest monk

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Re^2: creating defined references to arrays of size zero by spieper (Initiate) on Jul 14, 2005 at 07:53 UTC
strange-- I was doing that. I tried to recreate the code on my home computer and it worked as you all said (and as I originally expected it to). I'm guessing either a) my work has a weird version of perl b) the larger code I'm working on has some strange options set Thanks for all your help.	[reply]
Re^3: creating defined references to arrays of size zero by spieper (Initiate) on Jul 14, 2005 at 15:49 UTC
aha-- woke up and realized what I was doing-- definitely an ID 10-T error. Most of my keys were one letter, but one was actually a full word (I know the possible keys ahead of time), so I did something stupid like `hash = { a=>[]; b=>[] c=>[] . . . } #some time later my $key = "alpha" my $array = $hash->{$key};` [download] At this point there isn't anything at $hash->{$key}, so $array isn't pointing to anything real. When I push onto $array, that memory will get allocated happily, and won't create anything in the hash (which is a very good thing). If instead, the first thing I do is to shove something into @{$hash->{$key}}, a new entry gets magically allocated, and then everything works as expected. Obviously I'm not one with the perl yet.	[reply] [d/l]
Re^4: creating defined references to arrays of size zero by NetWallah (Canon) on Jul 14, 2005 at 17:32 UTC
This is precisely where tlm's suggestion(++) comes in handy: You could do: `my $array = $hash->{$key} \|\|=[];` [download] This would initialize the hash value to an empty array ref, when necessary. "Income tax returns are the most imaginative fiction being written today." -- Herman Wouk	[reply] [d/l]