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55 lines
1.9 KiB
Scheme
55 lines
1.9 KiB
Scheme
(module parser-actions mzscheme
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(require "grammar.ss")
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(provide (all-defined-except make-reduce make-reduce*)
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(rename make-reduce* make-reduce))
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;; An action is
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;; - (make-shift int)
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;; - (make-reduce prod runtime-action)
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;; - (make-accept)
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;; - (make-goto int)
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;; - (no-action)
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;; A reduce contains a runtime-reduce so that sharing of the reduces can
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;; be easily transferred to sharing of runtime-reduces.
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(define-struct action () (make-inspector))
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(define-struct (shift action) (state) (make-inspector))
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(define-struct (reduce action) (prod runtime-reduce) (make-inspector))
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(define-struct (accept action) () (make-inspector))
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(define-struct (goto action) (state) (make-inspector))
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(define-struct (no-action action) () (make-inspector))
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(define (make-reduce* p)
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(make-reduce p
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(vector (prod-index p)
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(gram-sym-symbol (prod-lhs p))
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(vector-length (prod-rhs p)))))
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;; A runtime-action is
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;; non-negative-int (shift)
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;; (vector int symbol int) (reduce)
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;; 'accept (accept)
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;; negative-int (goto)
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;; #f (no-action)
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(define (action->runtime-action a)
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(cond
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((shift? a) (shift-state a))
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((reduce? a) (reduce-runtime-reduce a))
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((accept? a) 'accept)
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((goto? a) (- (+ (goto-state a) 1)))
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((no-action? a) #f)))
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(define (runtime-shift? x) (and (integer? x) (>= x 0)))
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(define runtime-reduce? vector?)
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(define (runtime-accept? x) (eq? x 'accept))
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(define (runtime-goto? x) (and (integer? x) (< x 0)))
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(define runtime-shift-state values)
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(define (runtime-reduce-prod-num x) (vector-ref x 0))
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(define (runtime-reduce-lhs x) (vector-ref x 1))
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(define (runtime-reduce-rhs-length x) (vector-ref x 2))
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(define (runtime-goto-state x) (- (+ x 1)))
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)
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