Text::MeCab(3pm)

NAME
Text::MeCab - Alternate Interface To libmecab

SYNOPSIS
  use Text::MeCab;
  my $mecab = Text::MeCab->new({
    rcfile             => $rcfile,
    dicdir             => $dicdir,
    userdic            => $userdic,
    lattice_level      => $lattice_level,
    all_morphs         => $all_morphs,
    output_format_type => $output_format_type,
    partial            => $partial,
    node_format        => $node_format,
    unk_format         => $unk_format,
    bos_format         => $bos_format,
    eos_format         => $eos_format,
    input_buffer_size  => $input_buffer_size,
    allocate_sentence  => $allocate_sentence,
    nbest              => $nbest,
    theta              => $theta,
  });

  for (my $node = $mecab->parse($text); $node; $node = $node->next) {
     # See perdoc for Text::MeCab::Node for list of methods
     print $node->surface, "\n";
  }

  # use constants
  use Text::MeCab qw(:all);
  use Text::MeCab qw(MECAB_NOR_NODE);

  # check what mecab version we compiled against?
  print "Compiled with ", &Text::MeCab::MECAB_VERSION, "\n";

DESCRIPTION
libmecab (http://mecab.sourceforge.ne.jp) already has a perl interface built with it, so why a new module? I just feel that while a subtle difference, making the perl interface through a tied hash is just... weird.

So Text::MeCab gives you a more natural, Perl-ish way to access libmecab!

WARNING: Version 0.20015 has only been tested against libmecab 0.99.

INSTALLATION
You need to have mecab already installed. You also need a dictionary, such as ipadic.

Because we want to work with UTF-8 internally, we need to know what your dictionary's charset is. You need to tell our probe script (which gets invoked by Makefile.PL) interactively asks you this. If you want to specify it from elsewhere, you need to specify via environment variable:

    PERL_TEXT_MECAB_ENCODING=utf-8 perl Makefile.PL
    # or, say, you're using cpanm
    PERL_TEXT_MECAB_ENCODING=utf-8 cpanm Text::MeCab

If you want to build Text::MeCab with debugging info, specify it on the command line to Makefile.PL:

    perl Makefile.PL --debugging

Text::MeCab AND FORMATS
mecab allows users to specify an output format, via --*-format options. These are respected ONLY if you use the format() method:

  my $mecab = Text::MeCab->new({
    output_format_type => "user",
    node_format => "%m %pn"
  });

  for(my $node = $mecab->parse($text); $node; $node = $node->next) {
    print $node->format($mecab);
  }

Note that you also need to set the output_format_type parameter as well.

Text::MeCab AND SCOPING
[NOTE: The memory management issue has been changed since 0.09]

libmecab's default behavior is such that when you analyze a text and get a node back, that node is tied to the mecab "tagger" object that performed the analysis. Therefore, when that tagger is destroyed via mecab_destroy(), all nodes that are associated to it are freed as well.

Text::MeCab defaults to the same behavior, so the following won't work:

  sub get_mecab_node {
     my $mecab = Text::MeCab->new;
     my $node  = $mecab->parse($_[0]);
     return $node;
  }

  my $node = get_mecab_node($text);

By the time get_mecab_node() returns, the Text::MeCab object is DESTROY'ed, and so is $node (actually, the object exists, but it will complain when you try to access the node's internals, because the C struct that was there has already been freed).

In such cases, use the dclone() method. This will copy the *entire* node structure and create a new Text::MeCab::Node::Cloned instance.

  sub get_mecab_node {
     my $mecab = Text::MeCab->new;
     my $node  = $mecab->parse($_[0]);
     return $node->dclone();
  }

The returned Text::MeCab::Node::Cloned object is exactly the same as Text::MeCab::Node object on the surface. It just uses a different but very similar C struct underneath. It is blessed into a different namespace only because we need to use a different memory management strategy.

Do be aware of the memory issue. You WILL use up twice as much memory.

Also please note that if you try the first example, accessing the node *WILL* result in a segfault. This is *NOT* a bug: it's a feature :) While it is possible to control the memory management such that accessing a field in a node that has already expired results in a legal croak(), we do not go to the length to ensure this, because it will result in a performance penalty.

Just remember that unless you dclone() a node, then you are NOT allowed to access it when the original tagger goes out scope:

   {
       my $mecab = Text::MeCab->new;
       $node = $mecab->parse(...);
   }

   $node->surface; # segfault!!!!

Always remember to dclone() before doing this!

PERFORMANCE
Belows is the result of running tools/benchmark.pl on my PowerBook:

  daisuke@beefcake Text-MeCab$ perl tools/benchmark.pl
               Rate      mecab text_mecab
  mecab      5.53/s         --       -63%
  text_mecab 14.9/s       170%         --

METHODS

  new HASHREF | LIST
Creates a new Text::MeCab instance.

You can either specify a hashref and use named parameters, or you can use the exact command line arguments that the mecab command accepts.

Below is the list of accepted named options. See the man page for mecab for details about each option.

rcfile
dicdir
lattice_level
all_morphs
output_format_type
partial t =item node_format
unk_format
bos_format
eos_format
input_buffer_size
allocate_sentence
nbest
theta

  $node = $tagger->parse(SCALAR)
Parses the given text via mecab, and returns a Text::MeCab::Node object.

  $version = Text::MeCab::version()
The version number, as returned by libmecab's mecab_version();

  CONSTANTS

ENCODING
      my $encoding = Text::MeCab::ENCODING

    Returns the encoding of the underlying mecab library that was detected at compile time.

MECAB_VERSION
    The version number, same as Text::MeCab::version()

MECAB_TARGET_VERSION
    The version number detected at compile time of Text::MeCab.

MECAB_TARGET_MAJOR_VERSION
    The version number detected at compile time of Text::MeCab.

MECAB_TARGET_MINOR_VERSION
    The version number detected at compile time of Text::MeCab.

MECAB_CONFIG
    Path to mecab-config, if available.

MECAB_NOR_NODE
MECAB_UNK_NODE
MECAB_BOS_NODE
MECAB_EOS_NODE
MECAB_EON_NODE
MECAB_SYS_DIC
MECAB_USR_DIC
MECAB_UNK_DIC
MECAB_ONE_BEST
MECAB_NBEST
MECAB_PARTIAL
MECAB_MARGINAL_PROB
MECAB_ALTERNATIVE
MECAB_ALL_MORPHS
MECAB_ALLOCATE_SENTENCE

SEE ALSO
http://mecab.sourceforge.ne.jp

LICENSE
This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See http://www.perl.com/perl/misc/Artistic.html

AUTHOR
Copyright (c) 2006-2011 Daisuke Maki <daisuke@endeworks.jp> All rights reserved.