Here is an example that wraps create with a procedure that
adds 1 to all elements of the list that create returns.
#lang racket/base
(struct wrap (vals))
(define (create)
(displayln "A")
'(1 2 3))
(define create-wrap
(impersonate-procedure create
(lambda ()
(displayln "B")
(λ (result)
(displayln "C")
(displayln (list "Result: " result))
(map add1 result)))))
(create-wrap)
The result is:
B
A
C
(Result: (1 2 3))
'(2 3 4)
2015-08-21 1:44 GMT+02:00 Benjamin Greenman <benjaminlgreen...@gmail.com>:
> I'd like to change the result of a 0-arity function, but I need help
> crafting the right magic spell. Here's my attempt.
>
>
> #lang racket/base
>
> (struct wrap (vals)) ;; Wrap a list
> (define (create) '())
>
> (define create-wrap
> (impersonate-procedure create
> (lambda ()
> ;;(values)))) ;; -- this will run, but it doesn't wrap the result
> like I'd like.
> (values (lambda (r) (wrap r))
> (values)))))
>
> (create-wrap) ;; Error! result arity mismatch: expected 1, got 0.
>
> --
> You received this message because you are subscribed to the Google Groups
> "Racket Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to racket-users+unsubscr...@googlegroups.com.
> For more options, visit https://groups.google.com/d/optout.
>
--
--
Jens Axel Søgaard
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.
