That's the best solution I've come up with, which is basically the abstraction I suggested under #4.<div> </div><div>sam th On Sunday, September 25, 2011, Carl Eastlund wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"> How about we write a "define-toggle-contract-out" form, so everyone can define their own without actually implementing their own. Something like so: (define-toggle-contract-out my-contract-out #:disable) ;; comment out keyword to enable (provide (my-contract-out [thing thing/c])) Carl Eastlund On Sun, Sep 25, 2011 at 7:41 PM, J. Ian Johnson <<a>ianj@ccs.neu.edu</a>> 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 <<a>samth@ccs.neu.edu</a>> > To: J. Ian Johnson <<a>ianj@ccs.neu.edu</a>> > Cc: Matthew Flatt <<a>mflatt@cs.utah.edu</a>>, <a>dev@racket-lang.org</a> > 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 <<a>ianj@ccs.neu.edu</a>> 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 <<a>mflatt@cs.utah.edu</a>> >> To: <a>dev@racket-lang.org</a> >> 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: >> <a href="http://lists.racket-lang.org/listinfo/dev" target="_blank">http://lists.racket-lang.org/listinfo/dev</a> >> >> _________________________________________________ >> For list-related administrative tasks: >> <a href="http://lists.racket-lang.org/listinfo/dev" target="_blank"></a></blockquote></div> -- sam th <a href="mailto:samth@ccs.neu.edu">samth@ccs.neu.edu</a>