Has something changed in how `error` works across modules? This code that I
used last year without trouble seems to run into trouble now.
Here's the code all in one module:
#lang racket
(provide yield resume)
(define resumer #f)
(define (yield)
(let/cc k
(set! resumer k)
(error 'yield "yielding computation")))
(define (resume)
(resumer 'dummy))
(define (fact n)
(if (= n 0)
1
(begin
(when (= (remainder n 10) 0)
(yield))
(* n (fact (- n 1))))))
It results in the following (desired) interaction:
> (fact 10)
. . yield: yielding computation
> (resume)
3628800
But now I'm going to remove the definition of `fact` and put it in another
module, saving the remainder as `yielder.rkt`:
#lang racket
(require "yielder.rkt")
(define (fact n)
(if (= n 0)
1
(begin
(when (= (remainder n 10) 0)
(yield))
(* n (fact (- n 1))))))
Now I get the following error. What should I be doing instead?
> (fact 10)
-- #(struct:exn:fail:contract "vector-ref: contract violation\n expected:
vector?\n given: '((error 'yield \"yielding computation\")
#<path:/Users/sk/Desktop/yielder.rkt> 10 4 113 37)\n argument position:
1st\n other arguments...:\n 0" #<continuation-mark-set>)
(errortrace-stack-item->srcloc . #(struct:srcloc
#<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/stack-checkpoint.rkt> 168 0 6297
203))
(pick-first-defs . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/stack-checkpoint.rkt> 331 0 13000
425))
(get-exn-source-locs . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/stack-checkpoint.rkt> 585 0 23184
391))
(#f . #(struct:srcloc #<path:/Applications/Racket
v7.8/collects/racket/contract/private/arrow-val-first.rkt> 486 18 20735 32))
(error-display-handler/stacktrace . #(struct:srcloc
#<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/debug.rkt> 362 2 15076 2612))
(call-with-exception-handler . #(struct:srcloc
#<path:/Applications/Racket v7.8/collects/racket/private/more-scheme.rkt>
266 2 9251 256))
(fact . #(struct:srcloc #<path:/Users/sk/Desktop/client.rkt> 5 0 40 139))
(eval-one-top . #f)
(call-with-exception-handler . #(struct:srcloc
#<path:/Applications/Racket v7.8/collects/racket/private/more-scheme.rkt>
266 2 9251 256))
(loop . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/rep.rkt> 1210 24 50804 979))
(call-with-break-parameterization . #(struct:srcloc
#<path:/Applications/Racket v7.8/collects/racket/private/more-scheme.rkt>
148 2 4909 517))
(#f . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/rep.rkt> 1180 9 49153 5062))
(#f . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/drracket/drracket/private/rep.rkt> 1493 15 64385 1548))
(#f . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/gui-lib/mred/private/wx/common/queue.rkt> 435 6 19067 1056))
(#f . #(struct:srcloc #<path:/Applications/Racket
v7.8/share/pkgs/gui-lib/mred/private/wx/common/queue.rkt> 486 32 21054 120))
(call-with-break-parameterization . #(struct:srcloc
#<path:/Applications/Racket v7.8/collects/racket/private/more-scheme.rkt>
148 2 4909 517))
(eventspace-handler-thread-proc . #(struct:srcloc
#<path:/Applications/Racket
v7.8/share/pkgs/gui-lib/mred/private/wx/common/queue.rkt> 370 11 16515 690))
exception raised by error display handler: vector-ref: contract violation
expected: vector?
given: '((error 'yield "yielding computation")
#<path:/Users/sk/Desktop/yielder.rkt> 10 4 113 37)
argument position: 1st
other arguments...:
0; original exception raised: yield: yielding computation
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