From: "Stéphane Gimenez" <stephane.gimenez@pps.jussieu.fr>
To: The Caml Mailing List <caml-list@inria.fr>
Subject: type generalization of recursive calls
Date: Wed, 17 Feb 2010 17:34:24 +0100 [thread overview]
Message-ID: <20100217163424.GA38458@tenebreuse> (raw)
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
next reply other threads:[~2010-02-17 16:35 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-17 16:34 Stéphane Gimenez [this message]
2010-02-17 19:41 ` [Caml-list] " Boris Yakobowski
2010-02-17 20:25 ` Dario Teixeira
2010-02-17 20:33 ` Boris Yakobowski
2010-02-18 14:24 ` Stéphane Gimenez
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