[ANNOUNCE] New package typed-compose

[unlimitedscolobb]

Hello,

I am glad to announce typed-compose, a small package defining some utilities for composing functions in Typed Racket:

https://pkgd.racket-lang.org/pkgn/package/typed-compose

Typed Racket's compose only takes two arguments, because in general it is difficult to specify that the return types and the argument types should be the same for two successive functions in the argument list. This package defines some further utilities to allow compose-ing more than two functions more comfortable in Typed Racket.

This is my first ever Racket package, so I'm taking all kinds of feedback.

-

Sergiu

[philngu...@gmail.com]

Nice package. I don't have an account and don't know how to do pull request on Marvid thing, but I suggest making a macro generating `compose-n` for arbitrary (statically known) n, and export it along side with the predefined compose-n functions, something along these lines:

#lang typed/racket/base

(provide make-compose

         compose-3 compose-4)

(require (for-syntax racket/base

                     racket/match

                     racket/list

                     racket/syntax

                     syntax/parse))

(define-for-syntax (make-compose-type n)

  (with-syntax* ([(t ...) (generate-temporaries (make-list n 't))]

                 [a (generate-temporary 'a)]

                 [(_ ... t₀) #'(a t ...)]

                 [(F ...)

                  (let step ([u #'a] [ts (syntax->list #'(t ...))])

                    (match ts

                      ['() '()]

                      [(cons t ts*) (cons #`(#,t → #,u) (step t ts*))]))])

    #'(∀ (a t ...) (F ... → t₀ → a))))

(define-syntax make-compose

  (syntax-parser

    [(_ n:nat)

     (with-syntax* ([(f ...) (generate-temporaries (make-list (syntax-e #'n) 'f))]

                    [x (generate-temporary 'x)]

                    [T (make-compose-type (syntax-e #'n))]

                    [body (foldr (λ (fᵢ res) #`(#,fᵢ #,res)) #'x (syntax->list #'(f ...)))])

       #'(ann (λ (f ...) (λ (x) body)) T))]))

(define compose-3 (make-compose 3))

(define compose-4 (make-compose 4))

;; and so on

[unlimitedscolobb]

Thank you for the feedback!

I think this macro is a very nice idea and should indeed allow removing most compose-i functions, except maybe for compose-3 and compose-4, which can be examples of use of make-compose.

I added a Contributing section to the README of the Git repo: https://git.marvid.fr/scolobb/typed-compose#contributing . Do you think you can make the modifications directly a git clone of my repository and submit the changes to me as patches?

-

Sergiu