Wonderful!!! Thanks Sam,
-- Éric On Oct 25, 2011, at 5:17 PM, Sam Tobin-Hochstadt wrote: > On Sun, Oct 23, 2011 at 1:39 PM, Sam Tobin-Hochstadt <sa...@ccs.neu.edu> > wrote: >> >> Yes, I have planned to do this for a while. Probably the form it will >> take will be a macro that always produces a type error when checked, >> rather than a new type. Then macros could use this form to ensure >> exhaustiveness. > > This is now implemented in git. > > There's an `typecheck-fail' form which raises a type error when it is > reachable. Here's an example [1] > > (define-syntax (cond* stx) > (syntax-case stx () > [(_ x clause ...) > #`(cond clause ... [else (typecheck-fail #,stx "incomplete > coverage" #:covered-id x)])])) > > (: f : (U String Integer) -> Boolean) > (define (f x) > (cond* x > [(string? x) #t] > [(exact-nonnegative-integer? x) #f])) > > This produces a type error highlighting the `cond*' form, with the message: > > Type Checker: incomplete coverage; missing coverage of Negative-Integer in: > (cond* x ((string? x) #t) ((exact-nonnegative-integer? x) #f)) > > [1] https://gist.github.com/1314097 > -- > sam th > sa...@ccs.neu.edu > _________________________________________________ For list-related administrative tasks: http://lists.racket-lang.org/listinfo/users
