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Lucy::Analysis::Token – Apache Lucy Documentation
Apache Lucy™

NAME

Lucy::Analysis::Token - Unit of text.

SYNOPSIS

    my $token = Lucy::Analysis::Token->new(
        text         => 'blind',
        start_offset => 8,
        end_offset   => 13,
    );

    $token->set_text('mice');

DESCRIPTION

Token is the fundamental unit used by Apache Lucy’s Analyzer subclasses. Each Token has 5 attributes: text, start_offset, end_offset, boost, and pos_inc.

The text attribute is a Unicode string encoded as UTF-8.

start_offset is the start point of the token text, measured in Unicode code points from the top of the stored field; end_offset delimits the corresponding closing boundary. start_offset and end_offset locate the Token within a larger context, even if the Token’s text attribute gets modified – by stemming, for instance. The Token for “beating” in the text “beating a dead horse” begins life with a start_offset of 0 and an end_offset of 7; after stemming, the text is “beat”, but the start_offset is still 0 and the end_offset is still 7. This allows “beating” to be highlighted correctly after a search matches “beat”.

boost is a per-token weight. Use this when you want to assign more or less importance to a particular token, as you might for emboldened text within an HTML document, for example. (Note: The field this token belongs to must be spec’d to use a posting of type RichPosting.)

pos_inc is the POSition INCrement, measured in Tokens. This attribute, which defaults to 1, is a an advanced tool for manipulating phrase matching. Ordinarily, Tokens are assigned consecutive position numbers: 0, 1, and 2 for "three blind mice". However, if you set the position increment for “blind” to, say, 1000, then the three tokens will end up assigned to positions 0, 1, and 1001 – and will no longer produce a phrase match for the query "three blind mice".

CONSTRUCTORS

new

my $token = Lucy::Analysis::Token->new(
    text         => $text,          # required
    start_offset => $start_offset,  # required
    end_offset   => $end_offset,    # required
    boost        => 1.0,            # optional
    pos_inc      => 1,              # optional
);
  • text - A string.
  • start_offset - Start offset into the original document in Unicode code points.
  • start_offset - End offset into the original document in Unicode code points.
  • boost - Per-token weight.
  • pos_inc - Position increment for phrase matching.

METHODS

get_text

my $text = $token->get_text;

Get the token's text.

set_text

$token->set_text($text);

Set the token's text.

get_start_offset

my $int = $token->get_start_offset();

get_end_offset

my $int = $token->get_end_offset();

get_boost

my $float = $token->get_boost();

get_pos_inc

my $int = $token->get_pos_inc();

get_len

my $int = $token->get_len();

INHERITANCE

Lucy::Analysis::Token isa Clownfish::Obj.