treebank-parser/lib/passes.js

A simple parser for treebanks stored in S-Expressions

var json_utils = require(__dirname + '/json-utils');

exports.lex_sexp = function(input) {
  var regexp, symbols = [];

  for (var i=0; i<input.length; i++) {
    if ((regexp = (new RegExp('^\\s+')).exec(input.substring(i)))) {
      i += regexp[0].length-1;
    }
    else if ((regexp = (new RegExp('^\\(')).exec(input.substring(i)))) {
      symbols.push(regexp[0]);
    }
    else if ((regexp = (new RegExp('^[A-Za-z0-9_\\-\\$\\.\\,\\?\\!]+')).exec(input.substring(i)))) {
      symbols.push(regexp[0]);
      i += regexp[0].length-1;
    }
    else if ((regexp = (new RegExp('^\\)')).exec(input.substring(i)))) {
      symbols.push(regexp[0]);
    }
  }

  return symbols;
};

exports.convert_sexp_to_mexp = function(sexp_symbols) {
  var swap = false, mexp_symbols = [];

  for (var i=0; i<sexp_symbols.length; i++) {
    if (sexp_symbols[i] === '(') {
      swap = true;
    }
    else if (swap) {
      mexp_symbols = mexp_symbols.concat([sexp_symbols[i], '(']);
      swap = false;
    }
    else {
      mexp_symbols.push(sexp_symbols[i]);
    }
  }

  return mexp_symbols;
};

exports.convert_mexp_to_json = function(mexp_symbols) {
  var symbol = null, root_count = 0, sentence_count = 0, tree = {}, properties = [];

  for (var i=0; i<mexp_symbols.length; i++) {
    if (mexp_symbols[i] === '(') {
      properties.push(symbol);
      json_utils.set_tree_value(tree, properties, {});
      symbol = null;
    }
    else if (mexp_symbols[i] === ')') {
      if (symbol !== null) {
        json_utils.set_tree_value(tree, properties, json_utils.strip_duplicate_indicator(symbol));
        symbol = null;
      }
      properties.pop();
    }
    else if (symbol === null) {
      symbol = json_utils.get_property_name_for_duplicate(json_utils.get_node(tree, properties), mexp_symbols[i]);
    }
    else {
      json_utils.set_tree_value(tree, properties.concat(symbol), mexp_symbols[i]);
      symbol = null;
    }
  }

  return tree;
};