Array to hash refs

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

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Re: Array to hash refs by Abigail-II (Bishop) on Aug 13, 2002 at 16:01 UTC
`my @array = qw /a b c/; my $hash; my $val = 1; ($hash, $hash -> {pop @array}, $val) = (undef, $val, $hash) while @arr +ay > 1; $hash -> {pop @array} = $val;` [download] Abigail	[reply] [d/l]
Re: Re: Array to hash refs by BrowserUk (Patriarch) on Aug 14, 2002 at 08:06 UTC
Even with jeffa's notes below, it still took me a while to wrap this around my brain but when I had, I came up with this.... `my @array = qw /a b c d e f/; my $hash; my $val = 1; ($hash->{pop @array}, $val, $hash) = ($val, $hash, undef) while @array +; $hash = $val;` [download] Which is slightly cleaner?, but that final assignment stood out so... `my @array = qw /a b c d e f/; my $hash = 1; my $tmp; ($tmp->{pop @array}, $hash, $tmp) = ($hash, $tmp, undef) while @array +;` [download] Slightly non-intuative to assign the value to the hashref at the start but...	[reply] [d/l] [select]
Re: Re: Array to hash refs by aufrank (Pilgrim) on Aug 13, 2002 at 16:25 UTC
`my @array = qw /a b c/; my %hash = map {$_ => 1} @array; return \%hash;` [download] can that be done with a map and a hashref rather than having to return a hashref? ripped off from tadman in Re: an easier way with grep, map, and/or sort?. --au	[reply] [d/l]
Re: Array to hash refs by Abigail-II (Bishop) on Aug 13, 2002 at 16:28 UTC
`return {map {$_ => 1} qw /a b c/}` [download] Or did I understand your questing wrong? Abigail	[reply] [d/l]
(jeffa) Re: Array to hash refs by jeffa (Bishop) on Aug 13, 2002 at 16:06 UTC
Here is all i could come up with: `use strict; my @a = ('a'..'f'); my $hash; my $last = 1; for (reverse @a) { $hash->{$_} = $last; $last = {$_ => $hash->{$_}}; } delete $hash->{$a[$_]} for (1..@a);` [download] Hehehe, i waited until Abigail-II posted first though. Now i am going to spend some time figuring out how that works ... need more coffee! UPDATE: Ok, let's figure Abigail-II's code out ... When dealing with loops, a good way to understand the code is to chart out what happens at each iteration - Iteration 1: @array = ('a','b','c'); atomic: $hash = undef; $hash->{a} = $val; # $val = 1 $val = $hash; # is ('b','c') > 1 ? yes Iteration 2: @array = ('b','c'); atomic: $hash = undef; $hash->{b} = $val; # $val = {a => 1} $val = $hash; # is ('c') > 1 ? no Last line: (note that $hash is currently undef) $hash->{c} = $val; # $val = {b => {a => 1}} The key to this code is the atomic triple assignment inside the while loop. Break that into 3 seperate assignments and the results are not the same. Abigail-II++ :) UPDATE*2: I think i like Anony's answer the best ... now that is using Perl to write Perl! /smack forehead jeffa L-LL-L--L-LL-L--L-LL-L-- -R--R-RR-R--R-RR-R--R-RR B--B--B--B--B--B--B--B-- H---H---H---H---H---H--- (the triplet paradiddle with high-hat)	[reply] [d/l]
Re: (jeffa) Re: Array to hash refs by Abigail-II (Bishop) on Aug 14, 2002 at 09:18 UTC
You can break it into 4 separate assignments though.... Abigail	[reply]
Re: Array to hash refs by nat0m (Novice) on Aug 14, 2002 at 08:49 UTC
my solution: `use strict; my @array = qw/a b c d e f/; my $t = my $hashref = {}; while (@array) { $t = $t->{ shift @array } = @array>1 ? {} : 1 };` [download]	[reply] [d/l]
Re: Re: Array to hash refs by Anonymous Monk on Aug 14, 2002 at 11:27 UTC
Eval man! my @array = qw/a b c d/; my $ref = {}; $code = '$ref->{'.join('}->{', @array).'} = 1;'; eval $code; use Data::Dumper; print Dumper($ref);	[reply]
Re: Array to hash refs by Anonymous Monk on Aug 14, 2002 at 07:14 UTC
Thanks for all your help!	[reply]
Re: Array to hash refs by jackdied (Monk) on Aug 14, 2002 at 16:31 UTC
It sounds like you might be trying to write Tree::Trie, which creates a nested, searchable list based on the characters in it. Check it out, and also the thread word association problem -jackdied	[reply]
Re: Array to hash refs by deMize (Monk) on Oct 11, 2012 at 14:47 UTC
I got here from Google and this is old but: `$h={@arr};` And if you prefer `1` to `undef` then: `push @arr,1 if @arr % 2; $h={@arr};` [download] Nevermind: I misread the question, which was asking for a tree -- moderator, please delete this answer. Demize	[reply] [d/l] [select]