On Thursday, December 10, 2020 at 6:01:52 PM UTC+1 unlimitedscolobb wrote:
> On Thursday, December 10, 2020 at 5:49:43 PM UTC+1 hen...@topoi.pooq.com
> wrote:
>
> A macro might be able to generate either of the above from
>> (comp f g h k)
>> .
>>
> Indeed. I'm re-reading the docs on macros and I think I see a clean and
> clear way to achieve what I need.
>
> I'll post my attempt as soon as I get the time to write it.
>
>
Okay, so this is my shot:
#lang typed/racket
(require (for-syntax syntax/parse racket/match))
(define-syntax (multi-compose stx)
(syntax-parse stx
[(_ funcs:expr ...)
(match-define (list fn fn-1 fs ...)
(reverse (syntax->list #'(funcs ...))))
(datum->syntax stx (for/fold ([sexp `(compose ,fn-1 ,fn)])
([f (in-list fs)])
`(compose ,f ,sexp)))]))
(multi-compose f1 f2 ... fn-1 fn) expands to (compose f1 (compose f2 ( ...
(compose fn-1 fn) ... )))
My syntax-transformation-fu is essentially non-existent, even after reading
through Greg's Fear of Macros multiple times, so please do tell me if you
see some flagrant opportunities for improvement in the code above.
I'm planning to throw together a small package with compose-n , compose-3
to compose-10, and multi-compose, and publish it. It would normally be my
Christmas package for myself, but it make take some more time :-)
-
Sergiu
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