"{ Package: 'stx:goodies/smaCC' }"

"{ NameSpace: SmaCC }"

Object subclass:#SmaCCLR1Item

	instanceVariableNames:'rhs symbol location followers'

	classVariableNames:''

	poolDictionaries:''

	category:'SmaCC-Parser Generator'

!

SmaCCLR1Item comment:'SmaCCLR1Item represents an item in a SmaCCItemSet.

Instance Variables:

	followers	<SmaCCSymbolSet>	all possible symbols that can follow this production in this state

	location	<Integer>	the position in the rhs of the production we are at

	rhs	<SmaCCRHS>	the rhs of the production

	symbol	<SmaCCSymbol>	the symbol for the production'

!

!SmaCCLR1Item class methodsFor:'instance creation'!

symbol: productionGrammarSymbol rhs: aRHS follow: aGrammarSymbolCollection 

	^(self new)

		symbol: productionGrammarSymbol

			rhs: aRHS

			follow: aGrammarSymbolCollection;

		yourself

! !

!SmaCCLR1Item methodsFor:'accessing'!

action: aGrammarSymbol 

	location > rhs size 

		ifTrue: 

			[(symbol isStartingSymbol and: [aGrammarSymbol isEmptySymbol]) 

				ifTrue: [^SmaCCAcceptAction new].

			(followers includes: aGrammarSymbol) 

				ifTrue: [^SmaCCReduceAction symbol: symbol rhs: rhs]]

		ifFalse: [(rhs at: location) = aGrammarSymbol ifTrue: [^SmaCCShiftAction new]].

	^SmaCCRejectAction new

!

followers

	^followers

!

mergeWith: aLRItem 

	followers mergeWith: aLRItem followers

!

moveNext

	^(self copy)

		followers: (followers class basedOn: followers);

		location: location + 1;

		yourself

!

nextSymbol

	^location > rhs size 

		ifTrue: [SmaCCSymbol sentinel]

		ifFalse: [rhs at: location]

!

precedence

	"If we don't have a precedence, then assume we are the lowest precedence (which will cause a shift action)."

	| max |

	max := -1.

	rhs do: [:each | max := max max: (each precedence ifNil: [max])].

	^max

!

rest

	| newRHS |

	newRHS := SmaCCRHS new.

	location + 1 to: rhs size do: [:each | newRHS add: (rhs at: each)].

	^newRHS

! !

!SmaCCLR1Item methodsFor:'comparing'!

= anItem 

	^self class == anItem class and: 

			[location == anItem location 

				and: [rhs == anItem rhs and: [symbol == anItem symbol]]]

!

hash

	^(symbol identityHash bitXor: (location bitShift: 14)) 

		bitXor: rhs identityHash

! !

!SmaCCLR1Item methodsFor:'initialize-release'!

followers: aSymbolSet 

	followers := aSymbolSet

!

location: anInteger 

	location := anInteger

!

symbol: productionGrammarSymbol rhs: aRHS follow: aSymbolCollection 

	symbol := productionGrammarSymbol.

	rhs := aRHS.

	location := 1.

	followers := aSymbolCollection

! !

!SmaCCLR1Item methodsFor:'printing'!

printOn: aStream 

        | i |

        aStream

                nextPut: $[;

                nextPutAll: symbol printString;

                nextPutAll: ' :'.

        i := 1.

        rhs do: 

                        [:each | 

                        i = location ifTrue: [aStream nextPutAll: ' . ' asText allBold].

                        aStream

                                space;

                                nextPutAll: each printString.

                        i := i + 1].

        location > rhs size ifTrue: [aStream nextPutAll: ' . ' asText allBold].

        aStream nextPut: $;.

        followers printOn: aStream.

        aStream nextPut: $]

    "Modified: / 14-02-2008 / 12:28:48 / janfrog"

! !

!SmaCCLR1Item methodsFor:'private'!

location

	^location

!

rhs

	^rhs

!

symbol

	^symbol

! !

!SmaCCLR1Item methodsFor:'public'!

isLR1EqualTo: aLRItem 

	^self followers size = aLRItem followers size 

		and: [self followers allSatisfy: [:each | aLRItem followers includes: each]]

! !

!SmaCCLR1Item class methodsFor:'documentation'!

version

    ^ '$Header: /opt/data/cvs/stx/goodies/smaCC/SmaCC__SmaCCLR1Item.st,v 1.2 2008-02-17 10:30:47 vranyj1 Exp $'

! !