[racket] Contracts and submodules

1. Clutter removal is built into Racket: 

(define-syntax (interface stx)
  (syntax-case stx (subject-to)
    [(interface name clauses ...)
     ;; ==> 
     .. (provide (contract-out ..) ..) ..]))

The above macro has become a standard in my recent projects where I place it into my ./Lib/contract.rkt library. It is part of an effort to develop a header-file style for Racket. And it is an effort to supply a way to selectively check contracts. [More soon. It is NOT about turning contracts off.]

2. Contract test issue acknowledged. I have run into this problem too during my recent construction of a game program. My work-around 

3. Clutter removal is built into Racket: 

#lang racket

#lang racket

(define-syntax-rule
  (tmod def-or-exp ...)
  (module* test racket
    (require rackunit (submod ".."))
    (check-equal? 1 1)
    def-or-exp ...))

;; -----------------------------------------

(provide
 (contract-out
  (f (-> integer? integer?))))

(define (f x) x)

(tmod (check-equal? (f 2) 2)
      (check-equal? (f 3) 2))

Consider adding the above module to your ./Lib/contract.rkt library. 






On Mar 5, 2013, at 8:39 AM, Greg Hendershott wrote:

> Not to flog this, but:
> 
> Lately I've been trying to be a good little doobie and use `(provide
> (contract-out))` instead of `define/contract`. Although it's more
> typing/clutter, grumble grumble, I've been getting used to it.
> 
> Unfortunately I discovered one gotcha: Using (module+ test <rackunit
> tests>) means that the test bypasses the contract -- because it's a
> submodule, and the contract is on the module boundary. So my unit
> tests weren't exercising and validating the contract. I missed a buggy
> contract this way.
> 
> In hindsight this is all perfectly obvious. Just not from the guide.
> To be fair using submodules for tests is a relatively recent practice
> in Racket. But I wanted to point out the interaction in case it helps
> anyone else who is trying to use module contracts and do unit tests
> following the curent examples.
> 
> One way to avoid this problem is instead of module+ use module*:
> 
>  (module* test racket ;; To test module-boundary contracts, must use
>                       ;; module* and (require (submod "..")).
>    (require (submod ".."))
>    ... check check check ...
>    )
> 
> Of course this adds even more "clutter", but it works.
> 
> On Thu, Dec 27, 2012 at 3:31 PM, Matthias Felleisen
> <matthias at ccs.neu.edu> wrote:
>> 
>> I have added a note on this issue to the Style issue; see section 3.6. Strictly speaking, this prose probably belongs into the Contract guide. -- Matthias
>> 
>> 
>> 
>> On Nov 30, 2012, at 5:17 PM, Ryan Culpepper wrote:
>> 
>>> You can have mutually recursive functions with define/contract, but you can't with submodules.
>>> 
>>> Ryan
>>> 
>>> On 11/30/2012 05:04 PM, Ray Racine wrote:
>>>> Why not make this explicit by deprecating define/contract and support
>>>> this use case with a submodule.  They lightweight enough and makes
>>>> boundary demarcations consistent, explicit and simple.  Module -> boundary.
>>>> 
>>>> On Nov 30, 2012 12:05 PM, "Matthias Felleisen" <matthias at ccs.neu.edu
>>>> <mailto:matthias at ccs.neu.edu>> wrote:
>>>> 
>>>> 
>>>>   On Nov 30, 2012, at 10:15 AM, Greg Hendershott wrote:
>>>> 
>>>>>> This is a complete misunderstanding.
>>>>> 
>>>>> Sometimes I feel like a kid in the room while the adults are talking.
>>>>> When it comes to contracts, I have to stipulate that most of you are
>>>>> smarter than me and have thought about this longer than me.
>>>> 
>>>> 
>>>>   Apologies. My opening wasn't meant to say "I am smarter" but I wanted
>>>>   to send a strong message about define/contract. It really introduces a
>>>>   boundary and in some strange sense your (possibly misleading)
>>>>   microbenchmark
>>>>   exposes this constraint too.
>>>> 
>>>> 
>>>> 
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