# LeadingDistinct.pm                                        15jun15waw

# for each token in a set of tokens, find minimum leading
# substring that uniquely distinguishes the token
# from all other tokens in the set.

# works with Perl 5.8.9

package LeadingDistinct;

use warnings;
use strict;

use List::Util       qw(max);
use List::MoreUtils  qw(uniq);


sub extract {

    my (@tokens,
        ) = @_;

    @tokens = ('', uniq(sort @tokens), '');

    return
        map { $tokens[$_], distinguish(@tokens[ $_-1, $_, $_+1 ]) }
        1 .. $#tokens-1
        ;

    }


sub distinguish {

    my ($before,
        $word,
        $after,
        ) = @_;  # contiguous sequence of three alpha-sorted words

    return substr $word, 0, 1 + max diff($word, $before), diff($word, $after);

    }


sub diff {

    my ($w1,
        $w2,
        ) = @_;

    my $x = $w1 ^ $w2;

    $x =~ s{ [^\x00] .* \z }{}xms;

    return length $x;

    }

1;