[racket-dev] contract-out

Right now, in the Typed Racket implementation, there's forms like this:

(provide-cond-contract [foo foo?])

Option #2 would be something like this:

(provide (cond-contract-out enable-contracts? [foo foo?]))

and everywhere has to reference the `enable-contracts?' identifier.
I'm not convinced that this is that much nicer than rolling your own.

On Sun, Sep 25, 2011 at 7:41 PM, J. Ian Johnson <ianj at ccs.neu.edu> wrote:
> Everyone rolling their own is bad. We want people to contract their code, and they don't want to always pay for the overhead. #2 sounds the best, since that could be again abstracted over by the user, this time with one line instead of the sevel it takes to implement provide-cond-contract. This also has the advantage that the user can have access to any subforms someone else adds later.
> -Ian
> ----- Original Message -----
> From: Sam Tobin-Hochstadt <samth at ccs.neu.edu>
> To: J. Ian Johnson <ianj at ccs.neu.edu>
> Cc: Matthew Flatt <mflatt at cs.utah.edu>, dev at racket-lang.org
> Sent: Sun, 25 Sep 2011 11:34:39 -0400 (EDT)
> Subject: Re: [racket-dev] contract-out
>
> On Sun, Sep 25, 2011 at 10:55 AM, J. Ian Johnson <ianj at ccs.neu.edu> wrote:
>> Very nice! Is it easy to make a provide form that conditionally provides with contracts, such as Sam's provide-cond-contract in typed-scheme/utils/utils.rkt?
>
> The trouble with this is that it's not clear how it should be
> controlled.  There are a few obvious possibilities:
>
> 1. There's a global flag for all of Racket which turns contracts on
> and off.  It should be pretty clear that this is a bad idea.
> 2. There's a form like `(contract-cond-out expr stuff ...)'  which
> uses the contracts in `stuff' IFF `expr' is true.  This is easy to
> implement, but pretty inconvenient to use.
> 3. Something like the status quo, where everyone defines their own
> thing, but maybe with some abstraction.
> 4. A compiler flag.  We don't have anything like this, though,
> currently, and it's not clear how it should work.
>
>
>> -Ian
>> ----- Original Message -----
>> From: Matthew Flatt <mflatt at cs.utah.edu>
>> To: dev at racket-lang.org
>> Sent: Sat, 24 Sep 2011 09:41:17 -0400 (EDT)
>> Subject: [racket-dev] contract-out
>>
>> The `racket/contract' and `racket' modules now provide `contract-out',
>> which is a `provide' form for contracts. Use
>>
>>    (provide (contract-out ....))
>>
>> instead of
>>
>>    (provide/contract ....)
>>
>>
>> There's one difference between `(provide (contract-out ....))' and
>> `(provide/contract ....)': contract expressions in contract-out' are
>> implicitly moved to the end of the module, which means that they can
>> refer to variables that are defined later. For example, the following
>> program works as you'd expect:
>>
>>  #lang racket
>>
>>  (provide (contract-out [mask-of (turtle? . -> . color?)])
>>          turtle?
>>          color?)
>>
>>  (define (turtle? v)
>>   (memq v '(Leonardo Michelangelo Donatello Raphael)))
>>  (define (color? v)
>>   (memq v '(blue orange purple red)))
>>
>>  (define (mask-of t)
>>   (match t
>>     ['Leonardo 'blue]
>>     ['Michelangelo 'orange]
>>     ['Donatello 'purple]
>>     ['Raphael 'red]))
>>
>>
>> The `contract-out' form is implemented as a provide pre-transformer,
>> which is a new kind of `provide' form that is now supported by
>> `racket/provide-transform'.
>>
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://lists.racket-lang.org/listinfo/dev
>>
>> _________________________________________________
>>  For list-related administrative tasks:
>>  http://lists.racket-lang.org/listinfo/dev
>>
>
>
>
> --
> sam th
> samth at ccs.neu.edu
>
>



-- 
sam th
samth at ccs.neu.edu