Something is wrong when using 'trace' on '+' and then calling 'reduce' #437
Description
I haven't been able to find the root cause here, but I can show the symptom pretty well. The following works as intended:
$ perl -Ilib bin/bel
Language::Bel 0.63 -- msys.
> (set old-+ +)
(lit clo nil ns (foldr (fn (x y) (apply buildnum ((of c+ cddr) x y))) 0 ns))
> (def + (n1 n2) (pr "(+ " n1 " " n2 ")" \lf) (old-+ n1 n2))
> (reduce + '(1 2 3 4 5))
(+ 4 5)
(+ 3 9)
(+ 2 12)
(+ 1 14)
15
Pretty cool, eh?
And then the following doesn't:
(def prlf args
(atomic
(apply pr args)
(pr \lf)))
(set wrapped-fns-table (table))
(mac wrap (f w)
(letu (vf vw)
`(withs (,vf ,f
,vw ,w
w2 (fn args (apply ,vw (cons ,vf args))))
(set (wrapped-fns-table w2) ,vf
,f w2))))
(set *trace-depth* 0)
(mac trace (f)
`(wrap ,f
(fn (orig . args)
(repeat *trace-depth* (pr " "))
(pr "Entering (" (nom ',f))
(each a args
(pr " " a))
(prlf ")")
(++ *trace-depth*)
(let result (apply orig args)
(-- *trace-depth*)
(repeat *trace-depth* (pr " "))
(pr "Leaving " (nom ',f))
(prlf " ==> " result)
result))))
(trace +)
(reduce + '(1 2 3 4 5))
Gives the following output:
$ perl -Ilib bin/bel trace-plus.bel
Entering (+ 4 5)
Entering (+ 0 1)
Entering (+ 0 1)
Entering (+ 0 1)
Entering (+ 0 1)
I see three things that are wrong, offhand:
- The second entry should say
Entering (+ 3 9), just like thetrace-less version above. - We have
Enteringlines but notLeavinglines, despite the fact that the+function is called as part of thereducefunction does not contain any recursion. - We get stuck at the
(+ 0 1)case forever.
Even though I haven't confirmed it, I suspect this is another re-occurrence of #273. Somehow.