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Re: [Caml-list] type generalization of recursive calls
- Damien Guichard
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Date: | 2010-02-17 (18:13) |
From: | Damien Guichard <alphablock@o...> |
Subject: | Re: [Caml-list] type generalization of recursive calls |
I have to apologize because your definition is actually correct. Sorry i have read it too fast and didn't see map burried in type casting. It seems to me your are doing structural recursion on some binary tree structure. Presumably to fast-merge binary heaps or something like that. pa_polyrec is probably a must have for such things. - damien Le 17/02/2010 à 17:34:24, "Stéphane Gimenez" <stephane.gimenez@pps.jussieu.fr> à écrit : > >Hi, > >I just realized that ocaml generalizes the type of a recursively >defined function *only* for calls which are outside it's own >definition. Recursive calls cannot use a generalized type. > >In fact, I'm tring to work with such a data type: > >type 'a t = > | E > | D of 'a t * 'a t > | O of 'a > | I of 'a t t > >And, I'm forced to use some dark magic to define simple operations on >it: > >let rec map (f : 'a -> 'b) : 'a t -> 'b t = > begin function > | E -> E > | D (t1, t2) -> D (map f t1, map f t2) > | O a -> O (f a) > | I tt -> > I ((Obj.magic map : ('a t -> 'b t) -> 'a t t -> 'b t t) (map f) tt) > end > >Questions: > - Is it theoreticaly safe to generalize recursive calls ? > - Is there a syntactical trick to use generalized recursive calls ? > - Could such a generalization be added to the type checker ? > - Performance issues ? > - More obfusctated type checking errors ? > >In a related disscution I found, one asked about generalization >between mutualy recursive definitions (same problem). No answers, but >maybe I just lack pointers. > >Cheers, >Stéphane > >_______________________________________________ >Caml-list mailing list. Subscription management: >http://yquem.inria.fr/cgi-bin/mailman/listinfo/caml-list >Archives: http://caml.inria.fr >Beginner's list: http://groups.yahoo.com/group/ocaml_beginners >Bug reports: http://caml.inria.fr/bin/caml-bugs > -- Mail created using EssentialPIM Free - www.essentialpim.com