323 lines
14 KiB
Scheme
323 lines
14 KiB
Scheme
;step collector state machine (not yet implemented):
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;
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; datatype held-type = NO-HELD-STEP | SKIPPED-STEP | HELD(args)
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;
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; states: global state of held
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; global: held : held-type
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; edge-names: first, skipped-first, second, skipped-second, double, late-let
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;
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;transitions (& actions):
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;
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; held = NO-HELD-STEP :
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; first(x) : held := HELD(x)
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; skipped-first : held := SKIPPED-STEP
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; second(x) : trigger(NO-HELD-STEP, x), held := NO-HELD-STEP
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; this happens when evaluating unannotated code
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; skipped-second : held := NO-HELD-STEP
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; I believe this can also arise in unannotated code
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; double(x) : double-trigger(x), held := NO-HELD-STEP
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; late-let(x) : late-let-trigger(x), held := NO-HELD-STEP
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;
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; held = SOME(SKIPPED-STEP) :
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; first(x) : ERROR
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; skipped-first : ERROR
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; second(x) : held := NO-HELD-STEP
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; this happens e.g. for evaluation of top-level var bound to a procedure
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; skipped-second : held := NO-HELD-STEP
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; double(x) : ERROR
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; late-let(x) : ERROR
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;
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; held = SOME(HELD(args))
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; first(x) : ERROR
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; skipped-first : ERROR
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; second(x) : trigger(HELD(args),x), held = NO-HELD-STEP
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; skipped-second : held = NO-HELD-STEP
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; double(x) : ERROR
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; late-let(x) : ERROR
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(module model mzscheme
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(require (lib "contract.ss")
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(lib "etc.ss")
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(lib "match.ss")
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(lib "class.ss")
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(prefix a: "annotate.ss")
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(prefix r: "reconstruct.ss")
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"shared.ss"
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"marks.ss"
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"model-settings.ss"
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"macro-unwind.ss"
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"lifting.ss"
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;; for breakpoint display
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"display-break-stuff.ss")
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(define program-expander-contract
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((-> void?) ; init
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((or/c eof-object? syntax? (cons/c string? any/c)) (-> void?)
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. -> . void?) ; iter
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. -> .
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void?))
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(provide/contract
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[go (program-expander-contract ; program-expander
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(step-result? . -> . void?) ; receive-result
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(or/c render-settings? false/c) ; render-settings
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boolean? ; track-inferred-names?
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(or/c object? (symbols 'testing)) ;; FIXME: can do better: subclass of language% ; the language level
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(procedure? . -> . void?) ; run-on-drscheme-side
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. -> .
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void?)])
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; go starts a stepper instance
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; see provide stmt for contract
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(define (go program-expander receive-result render-settings
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track-inferred-names? language-level run-on-drscheme-side)
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;; finished-exps:
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;; (listof (list/c syntax-object? (or/c number? false?)( -> any)))
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;; because of mutation, these cannot be fixed renderings, but must be
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;; re-rendered at each step.
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(define finished-exps null)
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(define/contract add-to-finished
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((-> syntax?) (or/c (listof natural-number/c) false/c) (-> any)
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. -> . void?)
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(lambda (exp-thunk lifting-indices getter)
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(set! finished-exps
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(append finished-exps
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(list (list exp-thunk lifting-indices getter))))))
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;; the "held" variables are used to store the "before" step.
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(define held-exp-list no-sexp)
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(define held-step-was-app? #f)
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(define held-finished-list null)
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;; highlight-mutated-expressions :
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;; ((listof (list/c syntax? syntax?)) (listof (list/c syntax? syntax?))
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;; -> (list/c (listof syntax?) (listof syntax?)))
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;; highlights changes occurring due to mutation. This function accepts the
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;; left-hand-side expressions and the right-hand-side expressions, and
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;; matches them against each other to see which ones have changed due to
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;; mutation, and highlights these.
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;; POSSIBLE RESEARCH POINT: if, say, (list 3 4) is mutated to (list 4 5),
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;; should the 4 & 5 be highlighted individually or should the list as a
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;; whole be highlighted. Is either one "wrong?" equivalences between
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;; reduction semantics?
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;;
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;; 2005-11-14: punting. just highlight the whole damn thing if there are
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;; any differences. In fact, just test for eq?-ness.
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#;
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(define (highlight-mutated-expressions lefts rights)
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(if (or (null? lefts) (null? rights))
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(list lefts rights)
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(let ([left-car (car lefts)]
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[right-car (car rights)])
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(if (eq? (syntax-property left-car 'user-source)
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(syntax-property right-car 'user-source))
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(let ([highlights-added
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(highlight-mutated-expression left-car right-car)]
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[rest (highlight-mutated-expressions
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(cdr lefts) (cdr rights))])
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(cons (cons (car highlights-added) (car rest))
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(cons (cadr highlights-added) (cadr rest))))))))
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;; highlight-mutated-expression: syntax? syntax? -> syntax?
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;; given two expressions, highlight 'em both if they differ at all.
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;; notes: wanted to use simple "eq?" test... but this will fail when a
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;; being-stepped definition (e.g. in a let) turns into a permanent one.
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;; We pay a terrible price for the lifting thing. And, for the fact that
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;; the highlighting follows from the reductions but can't obviously be
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;; deduced from them.
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#;
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(define (highlight-mutated-expression left right)
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(cond
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;; if either one is already highlighted, leave them alone.
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[(or (stepper-syntax-property left 'stepper-highlight)
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(stepper-syntax-property right 'stepper-highlight))
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(list left right)]
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;; first pass: highlight if not eq?. Should be broken for local-bound
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;; things as they pass into permanence.
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[(eq? left right)
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(list left right)]
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[else (list (stepper-syntax-property left 'stepper-highlight)
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(stepper-syntax-property right 'stepper-highlight))]))
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;; mutated on receipt of a break, used in displaying breakpoint stuff.
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(define steps-received 0)
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(define break
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(opt-lambda (mark-set break-kind [returned-value-list #f])
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(set! steps-received (+ steps-received 1))
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;; have to be careful else this won't be looked up right away:
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(when (getenv "PLTSTEPPERUNSAFE")
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(let ([steps-received/current steps-received])
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(run-on-drscheme-side
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(lambda ()
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(display-break-stuff
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steps-received/current
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mark-set break-kind returned-value-list)))))
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(let* ([mark-list (and mark-set (extract-mark-list mark-set))])
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(define (reconstruct-all-completed)
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(map (match-lambda
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[`(,source-thunk ,lifting-indices ,getter)
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(match (r:reconstruct-completed
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(source-thunk) lifting-indices
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getter render-settings)
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[#(exp #f) (unwind exp render-settings)]
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[#(exp #t) exp])])
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finished-exps))
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;; (printf "break called with break-kind: ~a ..." break-kind)
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(if (r:skip-step? break-kind mark-list render-settings)
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(begin
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;; (printf " but it was skipped!\n")
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(when (or (eq? break-kind 'normal-break)
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;; not sure about this...
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(eq? break-kind 'nomal-break/values))
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(set! held-exp-list skipped-step)))
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(begin
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;; (printf "and it wasn't skipped.\n")
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(case break-kind
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[(normal-break normal-break/values)
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(begin
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(when (and (eq? break-kind 'normal-break)
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returned-value-list)
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(error 'break
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"broken invariant: normal-break can't have returned values"))
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(set! held-finished-list (reconstruct-all-completed))
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(set! held-exp-list
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(map (lambda (exp)
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(unwind exp render-settings))
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(maybe-lift
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(r:reconstruct-left-side
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mark-list returned-value-list render-settings)
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#f)))
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(set! held-step-was-app? (r:step-was-app? mark-list)))]
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[(result-exp-break result-value-break)
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(if (eq? held-exp-list skipped-step)
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;; don't render if before step was a skipped-step
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(set! held-exp-list no-sexp)
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(let* ([new-finished-list (reconstruct-all-completed)]
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[reconstructed
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(map (lambda (exp)
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(unwind exp render-settings))
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(maybe-lift
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(r:reconstruct-right-side
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mark-list returned-value-list render-settings)
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#f))]
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[result
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(if (eq? held-exp-list no-sexp)
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;; in this case, there was no "before" step, due
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;; to unannotated code. In this case, we make the
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;; optimistic guess that none of the finished
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;; expressions were mutated. It would be somewhat
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;; painful to do a better job, and the stepper
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;; makes no guarantees in this case.
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(make-before-after-result
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;; NB: this (... ...) IS UNRELATED TO
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;; THE MACRO IDIOM OF THE SAME NAME
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(list #`(... ...))
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(append new-finished-list reconstructed)
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'normal)
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(let*-values
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([(step-kind)
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(if (and held-step-was-app?
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(eq? break-kind 'result-exp-break))
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'user-application
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'normal)]
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[(left-exps right-exps)
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;; write this later:
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;; (identify-changed
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;; (append held-finished-list held-exps)
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;; (append new-finished-list reconstructed))
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(values (append held-finished-list
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held-exp-list)
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(append new-finished-list
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reconstructed))])
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(make-before-after-result
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left-exps right-exps step-kind)))])
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(set! held-exp-list no-sexp)
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(receive-result result)))]
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[(double-break)
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;; a double-break occurs at the beginning of a let's
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;; evaluation.
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(when (not (eq? held-exp-list no-sexp))
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(error
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'break-reconstruction
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"held-exp-list not empty when a double-break occurred"))
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(let* ([new-finished-list (reconstruct-all-completed)]
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[reconstruct-result
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(r:reconstruct-double-break mark-list render-settings)]
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[left-side (map (lambda (exp) (unwind exp render-settings))
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(maybe-lift (car reconstruct-result) #f))]
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[right-side (map (lambda (exp) (unwind exp render-settings))
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(maybe-lift (cadr reconstruct-result) #t))])
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;; add highlighting code as for other cases...
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(receive-result
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(make-before-after-result
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(append new-finished-list left-side)
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(append new-finished-list right-side)
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'normal)))]
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[(expr-finished-break)
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(unless (not mark-list)
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(error 'break
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"expected no mark-list with expr-finished-break"))
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;; in an expr-finished-break, the returned-vals hold (listof
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;; (list/c source lifting-index getter)) this will now include
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;; define-struct breaks, for which the source is the source
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;; and the getter causes an error.
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(for-each (lambda (source/index/getter)
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(apply add-to-finished source/index/getter))
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returned-value-list)]
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[else (error 'break "unknown label on break")]))))))
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(define maybe-lift
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(if (render-settings-lifting? render-settings)
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lift
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;; ... oh dear; model.ss should disable the double-break & late-let break when lifting is off.
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(lambda (stx dont-care) (list stx))))
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(define (step-through-expression expanded expand-next-expression)
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(let* ([annotated (a:annotate expanded break track-inferred-names?
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language-level)])
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(eval-syntax annotated)
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(expand-next-expression)))
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(define (err-display-handler message exn)
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(if (not (eq? held-exp-list no-sexp))
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(begin
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(receive-result
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(make-before-error-result (append held-finished-list held-exp-list)
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message))
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(set! held-exp-list no-sexp))
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(receive-result (make-error-result message))))
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(program-expander
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(lambda ()
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;; swap these to allow errors to escape (e.g., when debugging)
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(error-display-handler err-display-handler)
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#;(void)
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)
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(lambda (expanded continue-thunk) ; iter
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(r:reset-special-values)
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(if (eof-object? expanded)
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(begin
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(receive-result (make-finished-stepping)))
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(step-through-expression expanded continue-thunk))))))
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