[plt-scheme] rename-out with contract?

From: Chongkai Zhu (czhu at cs.utah.edu)
Date: Wed Feb 13 16:34:01 EST 2008

David Van Horn wrote:
> Chongkai Zhu wrote:
>> David Van Horn wrote:
>>> Is there an idiomatic way of renaming exports with contracts?  For 
>>> example:
>>>   #lang scheme
>>>   (provide/contract [f (number? . -> . number?)])
>>>   (provide (rename-out [f g]))
>>>   (define (f n) n)
>>> I'd like g to be an alias for f, which this does, but I also want g 
>>> to have the same contract as f.  And I don't want to 1) duplicate 
>>> the contract, 2) touch the existing provide/contract form for f.
>> #lang scheme
>> (define c (number? . -> . number?))
>> (provide/contract [f c])
>> (provide/contract (rename f g c))
>> (define (f n) n)
> This violates requirement 2.  What I really want is something like 
> (rename/contract f g).

If you only want to attach the contract on the module interface, then 
it's impossible to meet both requirement 1 and 2.

One option is to you attach the contract to f itself:

#lang scheme
(provide f)
(provide (rename-out [f g]))
(define/contract f
  (number? . -> . number?)
  (lambda (n) n))

But that means calls to f in the module is also contracted.


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