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Re: Re: Re: Any Point in Uploading Tie::SortedHash

by danger (Priest)
on Sep 06, 2003 at 17:57 UTC ( #289488=note: print w/ replies, xml ) Need Help??


in reply to Re: Re: Any Point in Uploading Tie::SortedHash
in thread Any Point in Uploading Tie::SortedHash

It isn't complicated at all, and you do not need any modules beyond DB_File itself (which is part of the standard distro).

Tieing to a DB_File BTREE is no harder than tie'ing to anything else --- to keep it in memory (instead of in a file) just use undef in place of the filename argument. You can easily supply custom sort routines (default is lexical sorting).

use DB_File; $DB_BTREE->{compare} = sub { $_[1] cmp $_[0] }; tie my %h, 'DB_File', undef, O_RDWR|O_CREAT, 0666, $DB_BTREE or die "DB_File tie failed: $!"; %h = 'a' .. 'z'; print "$_ : $h{$_}\n" for keys %h;


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Re: Re: Re: Re: Any Point in Uploading Tie::SortedHash
by Limbic~Region (Chancellor) on Sep 06, 2003 at 18:16 UTC
    danger,
    This looks potentially really cool and I would like to incorporate this technique as one of the possible options of my module. The problem is I can't seem to get DB_BTREE->{compare} to do anything meaningful. I get the same result no matter what I make the sort routine.
    #!/usr/bin/perl -w use strict; use DB_File; tie my %h, 'DB_File', undef, O_RDWR|O_CREAT, 0666, $DB_BTREE or die "DB_File tie failed: $!"; #$DB_BTREE->{compare} = sub { $h{$_[1]} <=> $h{$_[0]} }; #$DB_BTREE->{compare} = sub { $h{$_[0]} <=> $h{$_[1]} }; #$DB_BTREE->{compare} = sub { $_[0] cmp $_[1] }; #$DB_BTREE->{compare} = sub { $_[1] cmp $_[0] }; %h = ( 'John' => 33, 'Jacob' => 29, 'Jingle' => 15, 'Heimer' => 48, 'Smitz' => 12, ); print "$_ : $h{$_}\n" for keys %h;

    What am I missing? - L~R

      Set $DB_BTREE->{compare} before tieing the hash. However, accessing the tied hash in the compare routine leads to deep recursion (FETCH method uses the compare routine to navigate the tree).

        danger,
        While this sounded like a good thing, it doesn't provide near enough functionality for the purpose of my module.
      • Ability to change the sort routine on the fly
      • Ability to sort on anything to include values

        Thanks anyway - I learned something new which is always a good thing

        Cheers - L~R

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