org.metasyntactic.math.automata
Class LR1Item

java.lang.Object
  |
  +--org.metasyntactic.math.automata.Production
        |
        +--org.metasyntactic.math.automata.LR0Item
              |
              +--org.metasyntactic.math.automata.LR1Item

All Implemented Interfaces:

java.lang.Comparable, java.io.Serializable

public class LR1Item

extends LR0Item

An LR(1) item (item for short) of a grammar G is a production of G with a dot at some position of the right side. And a second component called the lookahead

See Also:

Serialized Form

Field Summary

protected java.lang.Object

lookahead

Fields inherited from class org.metasyntactic.math.automata.LR0Item

dotPosition

Fields inherited from class org.metasyntactic.math.automata.Production

variable, yield

Constructor Summary

LR1Item(LR1Item copy, int dotPosition)

LR1Item(java.lang.Object variable, Tuple yield, int dotPosition, java.lang.Object lookahead)

LR1Item(java.lang.Object variable, Tuple yield, java.lang.Object lookahead)

Method Summary

static java.util.Set	_goto(AugmentedGrammar G_prime, java.util.Set I, java.lang.Object X) Goto(I, X) is defined to be the closure of the set of all items [A → αX.Β] such that [A → α.XΒ] is in I.
static java.util.Set	closure(AugmentedGrammar G_prime, java.util.Set I) If I is a set of items for a grammar G, then closure(I) is the set of items constructed from I by the two rules: Initially, every item in I is added to closure(I) If A → α.BΒ is in closure(I) and B → γ is a production, then add the itm B → .γ to I, if is not already there.
boolean	equals(java.lang.Object o)
java.lang.Object	getLookahead()
int	hashCode()
static java.util.Set	items(AugmentedGrammar G_prime) Items returns the canonical collection of sts of LRItems for an augmented grammar G'
static void	main(java.lang.String[] args)
java.lang.String	toString()

Methods inherited from class org.metasyntactic.math.automata.LR0Item

getItems, getSymbolAtDot, isReduce, isShift

Methods inherited from class org.metasyntactic.math.automata.Production

compareTo, get, getVariable, getYield, toLatex

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

lookahead

protected java.lang.Object lookahead

Constructor Detail

LR1Item

public LR1Item(java.lang.Object variable,
               Tuple yield,
               int dotPosition,
               java.lang.Object lookahead)

LR1Item

public LR1Item(java.lang.Object variable,
               Tuple yield,
               java.lang.Object lookahead)

LR1Item

public LR1Item(LR1Item copy,
               int dotPosition)

Method Detail

getLookahead

public java.lang.Object getLookahead()

hashCode

public int hashCode()

Overrides:

hashCode in class LR0Item

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class LR0Item

toString

public java.lang.String toString()

Overrides:

toString in class LR0Item

items

public static java.util.Set items(AugmentedGrammar G_prime)

Description copied from class: LR0Item

Items returns the canonical collection of sts of LRItems for an augmented grammar G'

closure

public static java.util.Set closure(AugmentedGrammar G_prime,
                                    java.util.Set I)

Description copied from class: LR0Item

If I is a set of items for a grammar G, then closure(I) is the set of items constructed from I by the two rules:

1. Initially, every item in I is added to closure(I)
2. If A → α.BΒ is in closure(I) and B → γ is a production, then add the itm B → .γ to I, if is not already there. We apply the rule until no more new items can be added to closure(I).

Intuitively, A → α.Bβ in closure(I) indicates that, at some point in the parsing process, we think we might next see a substring derivable from BΒ as input. If B → γ is a production, we also expect we might see a substring drivable from γ at this point. For this reason we also include B → .γ in closure(I).

_goto

public static java.util.Set _goto(AugmentedGrammar G_prime,
                                  java.util.Set I,
                                  java.lang.Object X)

Description copied from class: LR0Item

Goto(I, X) is defined to be the closure of the set of all items [A → αX.Β] such that [A → α.XΒ] is in I. Intuitively, if I is the set of items that are valid for some viable prefix γ, then goto(I, X) is the set of items that are valid for the viable prefix X.

main

public static void main(java.lang.String[] args)