Re: How to transform a matrix into a hash??

I would not recommend using eval. What's wrong with the recursive solution you have? If you really want to eval:

use Data::Dumper;

my @start = (
    [qw( a b c )],
    [qw( a b d )],
    [qw( b b b )],
);
my %finish;
my $e = join '', map {
    join '', '$finish', ( map {qq{{'$_'}}} @$_ ), " = 1;\n"
} @start;

print $e, "\n";
eval $e;

print Dumper \%finish;
__END__
$finish{'a'}{'b'}{'c'} = 1;
$finish{'a'}{'b'}{'d'} = 1;
$finish{'b'}{'b'}{'b'} = 1;

$VAR1 = {
          'a' => {
                   'b' => {
                            'c' => 1,
                            'd' => 1
                          }
                 },
          'b' => {
                   'b' => {
                            'b' => 1
                          }
                 }
        };
[download]

Update: In addition to saying that eval is probably not the best way to do this, I should have added that my particular implementation is not as careful as it should be. If this were really to be used, it would be a good idea to (1) better quote the indices into the hash, and (2) check the value of $@ (aka $EVAL_ERROR if you use English, see perlvar) in case of error.

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Re^2: How to transform a matrix into a hash?? by ikegami (Patriarch) on Feb 05, 2008 at 18:00 UTC
Yikes! If you're going to use `eval` do a better job of converting your strings to literals! Better yet, don't use `eval` at all. `my %finish; for my $indexes (@start) { my $p = \\%finish; $p = \($$p->{$_}) for @$indexes; $$p = 1; }` [download] Data::Diver hides that mess away.	[reply] [d/l] [select]