kuromoji/src/viterbi/ViterbiLattice.js

JavaScript implementation of Japanese morphological analyzer

/*
 * Copyright 2014 Takuya Asano
 * Copyright 2010-2014 Atilika Inc. and contributors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

"use strict";

var ViterbiNode = require("./ViterbiNode");

/**
 * ViterbiLattice is a lattice in Viterbi algorithm
 * @constructor
 */
function ViterbiLattice() {
    this.nodes_end_at = [];
    this.nodes_end_at[0] = [ new ViterbiNode(-1, 0, 0, 0, "BOS", 0, 0, "") ];
    this.eos_pos = 1;
}

/**
 * Append node to ViterbiLattice
 * @param {ViterbiNode} node
 */
ViterbiLattice.prototype.append = function (node) {
    var last_pos = node.start_pos + node.length - 1;
    if (this.eos_pos < last_pos) {
        this.eos_pos = last_pos;
    }

    var prev_nodes = this.nodes_end_at[last_pos];
    if (prev_nodes == null) {
        prev_nodes = [];
    }
    prev_nodes.push(node);

    this.nodes_end_at[last_pos] = prev_nodes;
};

/**
 * Set ends with EOS (End of Statement)
 */
ViterbiLattice.prototype.appendEos = function () {
    var last_index = this.nodes_end_at.length;
    this.eos_pos++;
    this.nodes_end_at[last_index] = [ new ViterbiNode(-1, 0, this.eos_pos, 0, "EOS", 0, 0, "") ];
};

module.exports = ViterbiLattice;