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@ -66,7 +66,7 @@
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(set! return-stack (cons return-k return-stack))
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(basic:goto where)))
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(struct $line (number thunk) #:transparent)
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(struct $line (number thunk))
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(define-macro (line NUMBER . STATEMENTS)
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#'($line NUMBER (λ () (with-handlers ([end-line-signal? (λ _ #f)])
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. STATEMENTS))))
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@ -168,19 +168,16 @@
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#'(basic:for VAR START-VALUE END-VALUE 1)]
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[(_ VAR START-VALUE END-VALUE STEP-VALUE)
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#'(begin
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;; initialize the loop counter
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(statement VAR "=" START-VALUE)
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;; create a point for the `next` statement to return to, using a continuation
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(let/cc return-point-for-next
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(statement VAR "=" START-VALUE) ; initialize the loop counter
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(let/cc return-k ; create a return point
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(push-for-stack (cons 'VAR
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(procedure-rename
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(λ () ; thunk that increments counter & teleports back to beginning of loop
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(define next-val (+ VAR STEP-VALUE))
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(if (<= next-val END-VALUE)
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(begin
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(set! VAR next-val)
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(return-point-for-next #f)) ; return value for subsequent visits to line
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(pop-for-stack))) (format-datum "~a-incrementer" 'VAR))))
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(λ () ; thunk that increments counter & teleports back to beginning of loop
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(define next-val (+ VAR STEP-VALUE))
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(if (<= next-val END-VALUE)
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(begin
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(set! VAR next-val)
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(return-k #f)) ; return value for subsequent visits to line
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(pop-for-stack)))))
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#f))]) ; return value for first visit to line
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(define (handle-next [which #f])
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