Let's not piggy-back too much on this one change. First of all, I'm proposing a very simple change, albeit with potentially complex consequences; you've got a somewhat more complex design change in mind, but entirely backwards compatible. Second, you detect definitions by using "define" as a keyword? No, thank you, sir. Let me know when you have a design that allows arbitrary definitions. Personally I think this concept will work better as a new macro than an add-on for cond, because you're turning the already-overloaded test position, which can be an expression or a cond-specific keyword, into a triple-overload including definition special form names.
Carl Eastlund On Tue, Oct 2, 2012 at 10:11 AM, Jay McCarthy <jay.mccar...@gmail.com>wrote: > In addition to this, I want internal definitions in conds: > > (cond > [test1 body1] > (define var ...) > [(test2 var) body2] > [(test3 var) body3]) > > I have a macro that does these things: > > https://github.com/jeapostrophe/exp/blob/master/condd.rkt > > It's pretty cute > > Jay > > On Tue, Oct 2, 2012 at 7:58 AM, Carl Eastlund <c...@ccs.neu.edu> wrote: > > Oh, no, as far as a "does it work out of the box" experiment goes, it > fails. > > Racket doesn't even compile. I meant more along the lines of our > > immutable-cons experiment, where we fix a bunch of code and see how > > problematic the compatibility issue becomes over time. > > > > Carl Eastlund > > > > > > On Tue, Oct 2, 2012 at 9:56 AM, J. Ian Johnson <i...@ccs.neu.edu> wrote: > >> > >> This experiment should be easy to run, no? Change the default cond and > run > >> DrDr? > >> -Ian > >> ----- Original Message ----- > >> From: "Carl Eastlund" <c...@ccs.neu.edu> > >> To: "Racket Developers" <dev@racket-lang.org> > >> Sent: Tuesday, October 2, 2012 9:52:38 AM GMT -05:00 US/Canada Eastern > >> Subject: [racket-dev] Falling through cond clauses > >> > >> > >> I often wish cond would raise an exception if all the tests failed and > >> there were no else clause. I have taken to writing a macro to enforce > this; > >> I usually call it cond!. The void default for cond seems like an > >> un-Racketish holdover from primarily-imperative programming. With some > of > >> the other changes we've made in Racket, are we willing to consider > changing > >> the fall-through behavior of cond? It seems like an experiment worth > running > >> to me. > >> > >> If not, I would at least like to add an erroring version of cond > somewhere > >> in the language. It's a shame to have to keep writing such a primitive > >> feature. Right now in my dracula github repo I have cond! implemented in > >> racket/cond and re-exported from racket, but I'm not thrilled about > either > >> the location or the name. I kept it out of racket/base so I could > depend on > >> the syntax collection for good source location reporting in the error > >> message. > >> > >> Carl Eastlund > >> > >> _________________________ > >> Racket Developers list: > >> http://lists.racket-lang.org/dev > >> > > > > > > _________________________ > > Racket Developers list: > > http://lists.racket-lang.org/dev > > > > > > -- > Jay McCarthy <j...@cs.byu.edu> > Assistant Professor / Brigham Young University > http://faculty.cs.byu.edu/~jay > > "The glory of God is Intelligence" - D&C 93 > >
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