31 lines
1.0 KiB
Racket
31 lines
1.0 KiB
Racket
#lang typed/racket
|
|
|
|
(provide pairof?)
|
|
|
|
(require typed/racket/unsafe)
|
|
(unsafe-require/typed racket/function
|
|
[[identity unsafe-cast-function] (∀ (A) (→ Any A))])
|
|
(define-syntax-rule (unsafe-cast v t)
|
|
((inst unsafe-cast-function t) v))
|
|
|
|
(: pairof?* (∀ (A D) (→ Any
|
|
(→ Any Boolean : A)
|
|
(→ Any Boolean : D)
|
|
Boolean)))
|
|
(define (pairof?* v a? d?)
|
|
(and (pair? v)
|
|
(a? (car v))
|
|
(d? (cdr v))))
|
|
|
|
(define pairof?
|
|
;; Circumvent https://github.com/racket/typed-racket/issues/429
|
|
(unsafe-cast pairof?*
|
|
(∀ (A D) (→ Any
|
|
(→ Any Boolean : A)
|
|
(→ Any Boolean : D)
|
|
Boolean
|
|
:
|
|
;; Circumvent
|
|
;; https://github.com/racket/typed-racket/issues/488
|
|
#:+ (Pairof A D)
|
|
#:- (! (Pairof A D)))))) |