aima.core.logic.propositional.parsing

Class PLParser

java.lang.Object

aima.core.logic.common.Parser<Sentence>

aima.core.logic.propositional.parsing.PLParser

public class PLParser
extends Parser<Sentence>

Artificial Intelligence A Modern Approach (3rd Edition): Figure 7.7, page 244.
Implementation of a propositional logic parser based on:

 Sentence        -> AtomicSentence : ComplexStence
 AtomicSentence  -> True : False : P : Q : R : ... // (1)
 ComplexSentence -> (Sentence) | [Sentence]
                 :  ~Sentence
                 :  Sentence & Sentence
                 :  Sentence | Sentence
                 :  Sentence => Sentence
                 :  Sentence <=> Sentence
 
 OPERATOR PRECEDENCE: ~, &, |, =>, <=> // (2)
 

Figure 7.7 A BNF (Backus-Naur Form) grammar of sentences in propositional logic, along with operator precedences, from highest to lowest.

Note (1): While the book states 'We use symbols that start with an upper case letter and may contain other letters or subscripts' in this implementation we allow any legal java identifier to stand in for a proposition symbol.

Note (2): This implementation is right associative (tends to be more intuitive for this language), for example:

 A & B & C & D 
 
 will be parsed as:
 
 (A & (B & (C & D)))
 
 

Author:

Ciaran O'Reilly, Ravi Mohan

See Also:

SourceVersion.isIdentifier(CharSequence)

Field Summary

Fields inherited from class aima.core.logic.common.Parser

lookAheadBufferSize

Constructor Summary

Constructors

Constructor and Description
PLParser() Default Constructor.

Method Summary

Modifier and Type	Method and Description
Lexer	getLexer()
protected Sentence	parse() To be implemented by concrete implementations of this class.

Methods inherited from class aima.core.logic.common.Parser

consume, lookAhead, match, parse, parse

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

PLParser

public PLParser()

Default Constructor.

Method Detail

getLexer

public Lexer getLexer()

Specified by:

getLexer in class Parser<Sentence>

Returns:

an instance of the Lexer to be used by a concrete implementation of this class.

parse

protected Sentence parse()

Description copied from class: Parser

To be implemented by concrete implementations of this class.

Specified by:

parse in class Parser<Sentence>

Returns:

the root node of an abstract syntax tree representation of the the concrete input syntax that was parsed.