Imcompability on foldl. #2

New Issue

2017-05-11T03:24:08+01:00

yjqww6 commented

2017-05-11 03:24:08 +01:00

(Migrated from github.com)

with typed-map:
(foldl (λ (x [acc : (Rec R (U Null (Pairof R Positive-Index)))])
(cons acc (add1 x)))
'()
'(1 2 3))
returns
'(((() . 4) . 3) . 2)

But in untyped racket
(foldl (λ (x acc)
(cons acc (add1 x)))
'()
'(1 2 3))
returns
'(((() . 2) . 3) . 4)

It seems there is a typo on the definition of foldl
[(_ f init-acc lᵢ ...)
(with-syntax ([(argᵢ ...) (generate-temporaries #'(lᵢ ...))])
#'(foldr (λ (argᵢ ... arg-acc) (f argᵢ ... arg-acc)) init-acc lᵢ ...))])

which should be
[(_ f init-acc lᵢ ...)
(with-syntax ([(argᵢ ...) (generate-temporaries #'(lᵢ ...))])
#'(foldl (λ (argᵢ ... arg-acc) (f argᵢ ... arg-acc)) init-acc lᵢ ...))]))

with typed-map: (foldl (λ (x [acc : (Rec R (U Null (Pairof R Positive-Index)))]) (cons acc (add1 x))) '() '(1 2 3)) returns '(((() . 4) . 3) . 2) But in untyped racket (foldl (λ (x acc) (cons acc (add1 x))) '() '(1 2 3)) returns '(((() . 2) . 3) . 4) It seems there is a typo on the definition of foldl [(_ f init-acc lᵢ ...) (with-syntax ([(argᵢ ...) (generate-temporaries #'(lᵢ ...))]) #'(**foldr** (λ (argᵢ ... arg-acc) (f argᵢ ... arg-acc)) init-acc lᵢ ...))]) which should be [(_ f init-acc lᵢ ...) (with-syntax ([(argᵢ ...) (generate-temporaries #'(lᵢ ...))]) #'(**foldl** (λ (argᵢ ... arg-acc) (f argᵢ ... arg-acc)) init-acc lᵢ ...))]))

SuzanneSoy commented

2017-05-11 08:52:31 +01:00

(Migrated from github.com)

@yjqww6 Thanks for the report! I had some tests for foldl, but unfortunately managed to skip this particular case :-( .

There's a fix coming in a couple of minutes. Sorry for the delay (we're not on the same timezone it seems!).

@yjqww6 Thanks for the report! I had some tests for `foldl`, but unfortunately managed to skip this particular case :-( . There's a fix coming in a couple of minutes. Sorry for the delay (we're not on the same timezone it seems!).

Sign in to join this conversation.