kusamoji/src/viterbi/ViterbiLattice.js

Japanese morphological analyzer for Node.js — Viterbi tokenizer with mmap dict loading and pluggable POS-source strategy

"use strict";

let 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) {
    let last_pos = node.start_pos + node.length - 1;
    if (this.eos_pos < last_pos) {
        this.eos_pos = last_pos;
    }

    let 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 () {
    let 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;