Thanks Jonathan! I've seen -rectypes mentioned over the years and always glossed over it thinking "Ah, I'll never need that!" :P
Understandable that it's a good default to have disabled. I'll experiment first and if I like the results I'll try to limit compiling with -rectypes to the smallest bit of code using it. On Fri, Sep 9, 2011 at 5:31 PM, Jonathan Protzenko < [email protected]> wrote: > You can use equirecursive types, which can be enabled through the -rectypes > command-line switch. With that option, your example above type-checks. > However, these are not enabled by default for a variety of reasons, the most > important one being it makes it much easier to shoot yourself in the foot. > > Cheers, > > jonathan > > > On Sat 10 Sep 2011 01:14:46 AM CEST, Anthony Tavener wrote: > >> I was considering returning a couple of closures to help organize my UI >> code, essentially representing current UI mode by one of these closures. But >> then I run into a problem because the types are infinite (returns a >> function, which returns a function, ...) >> >> A simplified example: >> >> # let rec a () = printf "state a\n"; b >> and b () = printf "state b\n"; a >> >> Error: This expression has type unit -> unit -> 'a >> but an expression was expected of type 'a >> >> >> Is there a way I can do this? To express (or 'hide') the cyclic nature of >> the type resolution? >> >> I've considered using continuations, but that seems heavy-weight for what >> I'm looking to do. And as far as I can tell I'd need to leverage Oleg's >> delimcc (which I'd love to start using and wrap my head around -- but for a >> task worthy of it!). >> >> I can use a variant to represent states/modes and have a dispatcher which >> runs the right code... but this introduces what feels like an unnecessary >> layer of distraction. Returning the closure of the "next state" seems >> straightforward, but introduces cycles into the typing. :( >> >> I'm hoping I'm missing something simple. Thank-you for any assistance! >> >> -Tony >> >> -- Caml-list mailing list. Subscription management and archives: https://sympa-roc.inria.fr/wws/info/caml-list Beginner's list: http://groups.yahoo.com/group/ocaml_beginners Bug reports: http://caml.inria.fr/bin/caml-bugs
