As usual I didn't read the manual which is a little bit cryptic for a non
native speaker.
The signature of fodl is ('a -> 'b -> 'b) -> 'b -> 'a list -> 'b
I was used to the signature of List.fold_left of OCaml where the signature
is : ('a -> 'b -> 'a) -> 'a -> 'b list -> 'a
The arguments are reversed...
Thx
Le mardi 14 décembre 2021 à 20:11:26 UTC+1, Jens Axel Søgaard a écrit :
> Try reversing the order for arguments for both fp and f.
>
> /Jens Axel
>
> Den tir. 14. dec. 2021 kl. 19.48 skrev Cyrille DEUSS <cyrill...@gmail.com
> >:
>
>> #lang racket
>> (require racket/format)
>>
>> (define pp_number
>> (lambda (n)
>> (~a n #:width 6 #:align 'right #:left-pad-string "0")))
>>
>> (define fp
>> (lambda (s n)
>> (string-append (pp_number n) " + " s)))
>>
>> (define f
>> (lambda (s n)
>> (format "~a + ~a" n s)))
>>
>> (foldl f "" '(1 2 3))
>> ; works great !
>>
>> (foldl fp "" '(1 2 3))
>> ; and why not this one ?
>>
>> Thanks in advance.
>> Cyrille
>>
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>>
>
>
> --
> --
> Jens Axel Søgaard
>
>
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