61 lines
1.5 KiB
Smalltalk
61 lines
1.5 KiB
Smalltalk
"
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A memoized parser, for refraining redundant computations.
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Instance Variables:
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stream <PositionableStream> The stream of the associated memento objects.
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buffer <Array of: PPMemento> The buffer of memento objects.
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"
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Class {
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#name : 'PPMemoizedParser',
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#superclass : 'PPDelegateParser',
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#instVars : [
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'buffer',
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'identifier'
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],
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#category : 'PetitParser-Parsers'
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}
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{ #category : 'parsing' }
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PPMemoizedParser >> check: aPPContext [
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(identifier == aPPContext identifier)
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ifFalse: [ self reset: aPPContext ].
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]
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{ #category : 'operators' }
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PPMemoizedParser >> memoized [
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"Ther is no point in memoizing more than once."
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^ self
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]
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{ #category : 'operators' }
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PPMemoizedParser >> nonMemoized [
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^ parser
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]
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{ #category : 'parsing' }
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PPMemoizedParser >> parseOn: aPPContext [
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| memento contextMemento aStream |
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"TODO: JK memoizing needs review!"
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self check: aPPContext.
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contextMemento := aPPContext remember.
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memento := (buffer at: contextMemento ifAbsentPut: [ PPMemento new ]).
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memento contextMemento isNil
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ifTrue: [
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aStream := aPPContext stream.
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memento result: (aStream size - aStream position + 2 < memento count
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ifTrue: [ PPFailure message: 'overflow' context: aPPContext ]
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ifFalse: [ memento increment. parser parseOn: aPPContext ]).
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memento contextMemento: aPPContext remember ]
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ifFalse: [ aPPContext restore: memento contextMemento ].
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^ memento result.
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]
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{ #category : 'parsing' }
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PPMemoizedParser >> reset: aPPContext [
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buffer := Dictionary new.
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identifier := aPPContext identifier.
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]
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