epic.parser.repl.DSLGrammar.scala Maven / Gradle / Ivy

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package epic.parser.repl

/*
 Copyright 2012 David Hall

 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.
*/
import breeze.linalg._
import epic.trees.{LexicalProduction, Rule, BinaryRule, UnaryRule}
import epic.parser.{SimpleGrammar, Grammar, RuleTopology}
import epic.lexicon.UnsmoothedLexicon

/**
 * A DSL Grammar allows us to define simple weighted PCFG's quickly.
 * Useful for testing. See definition of simpleGrammar for an example.
 * @author dlwh
 */
object DSLGrammar {
  def grammar(rewrites: DSLGrammarPart*): SimpleGrammar[String, String, String] = {
    val binaryProductions = Counter2[String, BinaryRule[String], Double]
    val unaryProductions = Counter2[String, UnaryRule[String], Double]
    val lexicon = Counter2[String, String, Double]
    rewrites foreach {
      case DSLBRule(br, w) =>
        binaryProductions(br.parent, br) = w
      case DSLURule(ur, w) =>
        unaryProductions(ur.parent, ur) = w
      case DSLLex(a, word, w) =>
        lexicon(a, word) = w
    }


    val grammar = RuleTopology("S", binaryProductions, unaryProductions)
    val unsmoothed = new UnsmoothedLexicon(grammar.labelIndex, lexicon.keySet.toSet)
    Grammar.generative(grammar, unsmoothed, binaryProductions, unaryProductions, lexicon)
  }

  def simpleGrammar =  grammar(
    'S -> 'Sb -> 1.0,
    'Sb -> ('NPu, 'VPu) -> 1.0,

    'VPu -> 'VPb -> 1.0,
    'VPb -> ('Vu, 'NPu) -> 1.0,

    'NPu -> 'NPb -> 1.0,
    'NPu -> 'N -> 1.0,

    'NPb -> ('Nu, 'PPu) -> 1.0,

    'PPu -> 'PPb -> 1.0,
    'PPb -> ('Pu, 'Nu) -> 1.0,

    'Nu -> 'N -> 1.0,
    'Pu -> 'P -> 1.0,
    'Vu -> 'V -> 1.0,

  // lexicon
    'N -> "She" -> 1.0,
    'V -> "eats" -> 1.0,
    'N -> "pizza" -> 1.0,
    'P -> "without" -> 1.0,
    'N -> "anchovies" -> 1.0
  )

  val lexicon = IndexedSeq(
    LexicalProduction("N","She"),
    LexicalProduction("V","eats"),
    LexicalProduction("N","pizza"),
    LexicalProduction("P","without"),
    LexicalProduction("N","anchovies")
  )

}

/**
 * objects part of the dsl to create grammars nicely. You won't create these directly.
 */
sealed trait DSLGrammarPart
/** You won't use this directly. */
case class DSLBRule(rule: BinaryRule[String], weight: Double) extends DSLGrammarPart
/** You won't use this directly. */
case class DSLURule(rule: UnaryRule[String], weight: Double) extends DSLGrammarPart
/** You won't use this directly. */
case class DSLLex(sym: String, word: String, weight: Double) extends DSLGrammarPart

/**
 * contains implicits to create dsl grammars. You won't use this directly.
 */
object DSLGrammarPart {
  implicit def binaryRule(r: ((Symbol, (Symbol, Symbol)), Double)):DSLGrammarPart = r match {
    case ((a, (b, c)), w) => DSLBRule(BinaryRule(a.name, b.name, c.name), w)
  }

  implicit def unaryRule(r: ((Symbol, Symbol), Double)):DSLGrammarPart = r match {
    case ((a, b), w) => DSLURule(UnaryRule(a.name, b.name, IndexedSeq.empty), w)
  }

  implicit def lex(r: ((Symbol, String), Double)):DSLGrammarPart = r match {
    case ((a, b), w) => DSLLex(r._1._1.name, r._1._2, r._2)
  }
}