I'm working with Dave Herman's JavaScript package. I've found a problem and a workaround, but I want to make sure there's not an easier workaround before I convert a bunch of code. The following program illustrates the issue:
#lang racket/load
(module a racket
;; this formulation "works" (prints #t):
(define-struct/contract s ((a number?) (b number?)) #:transparent)
(provide (struct-out s))
;; this formulation does not work (prints #f):
#;(define-struct s (a b) #:transparent)
#;(provide/contract [struct s ([a number?]
[b number?])]
#;(struct-out s)))
(module b racket
(require 'a)
(define-values (type _) (struct-info (make-s 3 4)))
(printf "type: ~s\n" type)
(printf "eq? ~s\n"
(eq? type
struct:s)))
(require 'b)
The problem is that when a structure is defined using define-struct and then a
contract is provided at the boundary, the structure type returned by
struct-info doesn't compare to the exported struct's value using eq?. As the
code illustrates, I can work around this by pushing the contract down into the
definition of the structure itself.
Before I change many pairs of structure-definitions & contracts, is there some
other simpler way to make this code "work"--that is, print #t?
Thanks!
John
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