gi
Class LR1_Grammar

java.lang.Object
  gi.Lexicon
      gi.Grammar
          gi.LR0_Grammar
              gi.LR1_Grammar

Direct Known Subclasses:

ERE

public class LR1_Grammar

extends LR0_Grammar

This class implements an LR(1) parser around a Grammar. The parser adapts to changes in the underlying Grammar. Semantics in a phrase are evaluated during a bottom-up parse, from left to right after all subtrees rooted in the phrase have been constructed. Attributes throughout the phrase are available during evaluation. LR(1) parsing considers context-specific lookahead terminals to more accurately choose between applicable phrases. LR(1) parsing is the default method used for a Grammar around which no parser has been explicitly constructed, and is the recommended method.

Version:

1.2

Author:

© 1999-2004 Craig A. Rich <carich@csupomona.edu>

Nested Class Summary

(package private) static class	LR1_Grammar.Context This class implements an LR(1) Context.
(package private) static class	LR1_Grammar.Contexts This class implements a set of LR(1) Contexts.

Nested classes inherited from class gi.Grammar

Grammar.ParseTree, Grammar.Production, Grammar.Semantics

Nested classes inherited from class gi.Lexicon

Lexicon.Alphabet, Lexicon.Concatenation, Lexicon.Exception, Lexicon.Expression, Lexicon.Match, Lexicon.NonMatch, Lexicon.PosixClass, Lexicon.Range, Lexicon.Repetition, Lexicon.Set, Lexicon.Singleton, Lexicon.Stack, Lexicon.UnicodeCategory, Lexicon.Union

Field Summary

Fields inherited from class gi.LR0_Grammar

S$, states, trees

Fields inherited from class gi.Grammar

CONFLICT, FIRST_FOLLOW, P, PARSE_TREE, S, SYNTAX

Fields inherited from class gi.Lexicon

$, debug, LEXICAL, TERMINALS, VERBOSE

Constructor Summary

protected	LR1_Grammar() Constructs an LR(1) parser around a new empty Grammar.
protected	LR1_Grammar(Grammar G) Constructs an LR(1) parser around an existing Grammar.

Method Summary

(package private) LR0_Grammar.Contexts	closure(LR0_Grammar.Contexts C) Computes the reflexive transitive closure of a set of LR(1) Contexts under empty transition.
(package private) Lexicon.Set	expected(LR0_Grammar.Contexts C) Computes the terminals expected in a set of LR(1) Contexts.
(package private) LR0_Grammar.Contexts	initial() Computes the initial state of the LR(1) DFA.
(package private) Grammar.Production	parse(LR0_Grammar.Contexts C, Object a) Computes the Production to use in a reverse rightmost derivation.
String	toString() Returns the string representation of this parser, specifically "LR(1)".
(package private) LR0_Grammar.Contexts	transition(LR0_Grammar.Contexts C, Object X) Computes a transition from a set of LR(1) Contexts on a symbol.

Methods inherited from class gi.LR0_Grammar

interpret

Methods inherited from class gi.Grammar

first, first, first, follow, grab, interpret, nonterminal, put, put, terminal

Methods inherited from class gi.Lexicon

expression, interpret, interpret, interpret, interpret, interpret, interpret, put, word

Methods inherited from class java.lang.Object

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

Constructor Detail

LR1_Grammar

protected LR1_Grammar()

Constructs an LR(1) parser around a new empty Grammar.

LR1_Grammar

protected LR1_Grammar(Grammar G)

Constructs an LR(1) parser around an existing Grammar.

Parameters:

G - the Grammar around which the parser is constructed.

Method Detail

closure

LR0_Grammar.Contexts closure(LR0_Grammar.Contexts C)

Computes the reflexive transitive closure of a set of LR(1) Contexts under empty transition.

Overrides:

closure in class LR0_Grammar

Parameters:

C - the set of LR(1) Contexts whose reflexive transitive closure is computed under empty transition.

Returns:

the reflexive transitive closure of from under empty transition.

expected

Lexicon.Set expected(LR0_Grammar.Contexts C)

Computes the terminals expected in a set of LR(1) Contexts.

Overrides:

expected in class LR0_Grammar

Parameters:

C - the set of LR(1) Contexts.

Returns:

the terminals matching a shift or reduce Context in C.

initial

LR0_Grammar.Contexts initial()

Computes the initial state of the LR(1) DFA.

Overrides:

initial in class LR0_Grammar

parse

Grammar.Production parse(LR0_Grammar.Contexts C,
                         Object a)

Computes the Production to use in a reverse rightmost derivation.

Overrides:

parse in class LR0_Grammar

Parameters:

C - the set of LR(1) Contexts.

a - the lookahead terminal.

Returns:

the highest priority Production underlying an applicable reduce Context in C; returns null if none.

toString

public String toString()

Returns the string representation of this parser, specifically "LR(1)".

Overrides:

toString in class LR0_Grammar

Returns:

the string representation of this parser, specifically "LR(1)".

Since:

1.1

transition

LR0_Grammar.Contexts transition(LR0_Grammar.Contexts C,
                                Object X)

Computes a transition from a set of LR(1) Contexts on a symbol.

Overrides:

transition in class LR0_Grammar

Parameters:

C - the set of LR(1) Contexts from which the transition is made.

X - the symbol on which the transition is made.

Returns:

the set of LR(1) Contexts to which the transition is made.