Hi,
I recently started learning Racket and like it so far. Since I very much prefer
statically typed languages, I am leaning towards Typed Racket.
In a small program I am writing I would like to have a function that accepts a
value of an abstract type and then calls a function on that type whose
implementation depends on the concrete type. I.e., what would be an interface
in Java with several classes implementing it or a type class in Haskell with
several instances.
In vanilla Racket it seems that I could use generic interfaces or class-based
interfaces, but in TR neither of these options seems to work. The following
works:
#lang typed/racket
;; "Interface"
(define-type X
(Object [get-name (-> String)]))
;; Implementation 1
(define A%
(class object%
(super-new)
(init-field [name : String])
(: get-name (-> String))
(define/public (get-name)
(~a "I am an A% and my name is " name "."))))
;; Implementation 2
(define B%
(class object%
(super-new)
(init-field [name : String])
(: get-name (-> String))
(define/public (get-name)
(~a "I am a B% and my name is " name "."))))
(: display-name (-> X Void))
(define (display-name x)
(displayln (send x get-name)))
(display-name (make-object A% "Alice")) ;; -> I am an A and my name is Alice.
(display-name (make-object B% "Bob")) ;; -> I am a B and my name is Bob.
– but I am not completely happy about it. Is there an idiomatic way to achieve
what I described in TR?
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