[Haskell-cafe] Re: The Worker/Wrapper Transformation

[Achim Schneider]

Achim Schneider <barsoap at web.de> wrote:

> (define (cons x y)
>    (lambda (m) (m x y)))
>  
> (define (car z)
>    (z (lambda (p q) p)))
> 
> (define (cdr z)
>    (z (lambda (p q) q)))
> 
, which, just for completeness, can be of course also be done in
Haskell:

cons :: a -> b -> (a -> b -> c) -> c
cons x y m = m x y

car :: ((a -> b -> a) -> c) -> c 
car z = z $ \p q -> p

cdr :: ((a -> b -> b) -> c) -> c
cdr z = z $ \p q -> q

Prelude> car $ cdr $ cdr $ cons 1 $ cons 2 $ cons 3 ()
3


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