40 lines
1.3 KiB
Smalltalk
40 lines
1.3 KiB
Smalltalk
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A lazy repeating parser, commonly seen in regular expression implementations. It limits its consumption to meet the 'limit' condition as early as possible.
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This class essentially implements the iterative version of the following recursive parser composition:
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| parser |
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parser := PPChoiceParser new.
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parser setParsers: (Array
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with: (limit and ==> [ :each | OrderedCollection new ])
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with: (self , parser map: [ :each :rest | rest addFirst: each; yourself ])).
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^ parser ==> [ :rest | rest asArray ]
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"
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Class {
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#name : 'PPLazyRepeatingParser',
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#superclass : 'PPLimitedRepeatingParser',
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#category : 'PetitParser-Parsers'
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}
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{ #category : 'parsing' }
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PPLazyRepeatingParser >> parseOn: aPPContext [
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| memento element elements |
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memento := aPPContext remember.
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elements := OrderedCollection new.
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[ elements size < min ] whileTrue: [
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(element := parser parseOn: aPPContext) isPetitFailure ifTrue: [
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aPPContext restore: memento.
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^ element ].
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elements addLast: element ].
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[ self matchesLimitOn: aPPContext ] whileFalse: [
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elements size < max ifFalse: [
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aPPContext restore: memento.
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^ PPFailure message: 'overflow' context: aPPContext at: memento position ].
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element := parser parseOn: aPPContext.
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element isPetitFailure ifTrue: [
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aPPContext restore: memento.
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^ element ].
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elements addLast: element ].
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^ elements asArray
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]
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