<to...@tuxteam.de> writes: >> (define (fn l) >> (define (ok l) >> (or (and (pair? l) l) >> (error "list is empty"))) >> (cons (reverse (car l)) (ok l))) > (so in my case it's 25 instead of 22). Interestingly, my version also > produces warnings about possibly unbound variables). If I enter the > code line by line into a repl, I also get a "not found 22". > > Interestingly, if I add a call to fn to the end of that snippet > (e.g. (fn '(a b))), the "not found" disappears. The unbound var > warnings stay.
Also interesting: I can primitive-eval the code:
(define code '(define (fn l)
(define (ok l)
(or (and (pair? l) l)
(error "list is empty")))
(cons (reverse (car l)) (ok l))))
(primitive-eval code)
(fn '((1 2))) ;; => ((2 1) (1 2))
What might be happening here is control flow analysis discarding
impossible branches:
(car l) will throw an error when l is not a pair. Since arguments are
evaluated in order, (ok l) will always succeed. This means (ok l) can be
replaced by l.
To look into details:
(compile code) ;; => throws an error: not found 22
;; use ,bt to get:
,bt
In system/base/compile.scm:
352:28 17 (compile _ #:from _ #:to _ #:env _ #:optimization-level _
#:warning-level _ #:opts _)
265:44 16 (_ _ _)
265:44 15 (_ _ _)
261:33 14 (_ #<intmap 0-83> #<module (#{ g836}#) 7fcbf85dfbe0>)
In language/cps/optimize.scm:
130:12 13 (_ _ _)
102:3 12 (optimize-higher-order-cps _ _)
In language/cps/type-fold.scm:
775:16 11 (type-fold _)
In language/cps/renumber.scm:
170:36 10 (renumber #<intmap 0-4,6-21,52-53> _)
166:30 9 (compute-renaming _ _)
144:7 8 (visit-fun _ _ _)
160:19 7 (visit-fun 12 #<transient-intmap 0-4,6-11> #<transient-intmap
0-3,5-6>)
In language/cps/utils.scm:
245:39 6 (compute-predecessors #<intmap 0-4,6-21,52-53> _ #:labels _)
107:3 5 (compute-function-body _ _)
129:30 4 (visit-cont _ _)
129:30 3 (visit-cont _ _)
112:9 2 (visit-cont 22 _)
In language/cps/intmap.scm:
397:51 1 (_ _)
In ice-9/boot-9.scm:
1685:16 0 (raise-exception _ #:continuable? _)
I’ll leave further steps to folks who are more experienced with
optimize-higher-order-cps (or want to become more experienced with it).
Best wishes,
Arne
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heißt politisch sein,
ohne es zu merken.
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