Fri 07 May 2010 09:48:31 AM UTC, original submission:
Consider this procedure of one optional argument:
#v+
scheme@(guile-user)> (define* (foo #:optional y) (baz))
scheme@(guile-user)> (program-sources foo)
$25 = ((25 #f 64 . 28))
scheme@(guile-user)> ,x foo
Disassembly of #<procedure foo (#:optional y)>:
0 (assert-nargs-ge 0 0)
3 (bind-optionals 0 1)
6 (assert-nargs-ee 0 1)
9 (reserve-locals 0 1)
12 (local-bound? 0)
14 (br-if :L730) ;; -> 21
18 (make-false)
19 (local-set 0) ;; `y'
21 (toplevel-ref 1) ;; `baz'
23 (tail-call 0) at (unknown file):64:28
#v-
Its program source info points at IP 25 whereas its last IP is 23. In addition, it has no info associated with IP 0, which single-arity procedures always have AFAICS.
The latter is solved when using `lambda*', but not the former:
#v+
scheme@(guile-user)> (define foo (lambda* (#:optional y) (baz)))
scheme@(guile-user)> (program-sources foo)
$26 = ((0 #f 67 . 12) (25 #f 67 . 36))
scheme@(guile-user)> ,x foo
Disassembly of #<procedure foo (#:optional y)>:
0 (assert-nargs-ge 0 0)
3 (bind-optionals 0 1)
6 (assert-nargs-ee 0 1)
9 (reserve-locals 0 1)
12 (local-bound? 0)
14 (br-if :L757) ;; -> 21
18 (make-false)
19 (local-set 0) ;; `y'
21 (toplevel-ref 1) ;; `baz'
23 (tail-call 0) at (unknown file):67:36
#v-
Finally, using `case-lambda' leads to different code, with more source info, but again with one IP off (19 instead of 17):
#v+
scheme@(guile-user)> (define foo (case-lambda (() (baz)) ((y) (baz))))
scheme@(guile-user)> (program-sources foo)
$27 = ((0 #f 70 . 12) (13 #f 70 . 29) (15 #f 70 . 12) (19 #f 70 . 41))
scheme@(guile-user)> ,x foo
Disassembly of #<procedure foo () | (y)>:
0 (br-if-nargs-ne 0 0 :L785) ;; -> 13
6 (reserve-locals 0 0)
9 (toplevel-ref 1) ;; `baz'
11 (tail-call 0) at (unknown file):70:29
13 (assert-nargs-ee/locals 1) at (unknown file):70:12
15 (toplevel-ref 1) ;; `baz'
17 (tail-call 0) at (unknown file):70:41
#v-
Ludo'.
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