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19 lines
441 B
Racket
19 lines
441 B
Racket
8 years ago
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#lang br
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(require "structs.rkt" "line.rkt")
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(provide b-goto b-gosub b-return)
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(define (b-goto num-expr)
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(raise (change-line-signal num-expr)))
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(define return-stack empty)
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(define (b-gosub num-expr)
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(let/cc return-cc
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(push! return-stack return-cc)
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(b-goto num-expr)))
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(define (b-return)
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(unless (pair? return-stack)
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(raise-line-error "return without gosub"))
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(define top-return-k (pop! return-stack))
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(top-return-k))
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