Hello,
I've found out that compose in Typed Racket has the type
(: compose (All (a b c) (-> (-> b c) (-> a b) (-> a c))))
which means that Typed Racket's compose can only combine two functions at a
time.
In untyped code, I tend to use compose to combine more functions (e.g., 7),
so I wrote myself the following definitions:
(: compose-n (All (a) (-> (-> a a) * (-> a a))))
(define (compose-n . funcs)
(λ (x)
(for/foldr ([x x]) ([f funcs])
(f x))))
(: compose-3 (All (a b c d) (-> (-> c d) (-> b c) (-> a b) (-> a d))))
(define (compose-3 f1 f2 f3)
(λ (x) (f1 (f2 (f3 x)))))
(: compose-4 (All (a b c d e) (-> (-> d e) (-> c d) (-> b c) (-> a b) (-> a
e))))
(define (compose-4 f1 f2 f3 f4)
(λ (x) (f1 (f2 (f3 (f4 x))))))
Is there a better way to chain compose calls in Typed Racket?
If the answer is no, is there any interest in including these three
functions (as well as compose-5, 6, 7, 8) into Typed Racket?
-
Sergiu
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