From: "Beck01, Wolfgang" <BeckW@t-systems.com>
To: caml-list@inria.fr
Subject: RE: [Caml-list] strange behaviour with variants and "cannot be g eneralized"
Date: Tue, 9 Sep 2003 16:13:29 +0200 [thread overview]
Message-ID: <ADD42C8394EBD4118A3D0003470C18F00950F3D7@G9JJT.mgb01.telekom.de> (raw)
>
>
> From: "Beck01, Wolfgang" <BeckW@t-systems.com>
>
> > v1.ml ----------------------------
> >
> > open Vtop
> >
> > type t = {
> > v1_x : int array;
> > }
> >
> > let init = `V1 { v1_x = [| 0 |] }
> Sure: [| 0 |] creates a mutable data structure, and as such is
> considered as a side-effecting expression. As a result the type of
> init cannot be generalized.
Funnily, I just found a workaround:
v1.ml ----------------------------
open Vtop
type r_t = {
r_a : int array;
}
type t = {
v1_x : r_a;
}
let r_init = { r_a = Array.make 100 0 }
let init = `V1 { v1_x = r_init }
----------------------------------
compiles. However, "let init = `V1 { v1_x = { r_a = Array.make 100 0 }} "
does not.
>
> OCaml 3.07 is more clever about that, and the above program would be
> accepted with no problem.
>
Good to hear. I have introduced variants im my major project after playing
around with toy programs like the one above. But I did not check if
arrays would work. After a week of rearranging my code, I successfully
implemented my first real-world variant (without an array). Then, I
started a second one yesterday and was quite upset when I found that
it did not compile (it took me some time to find that arrays were causing
the trouble).
Regards,
Wolfgang Beck
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next reply other threads:[~2003-09-09 14:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-09 14:13 Beck01, Wolfgang [this message]
2003-09-09 19:17 ` Didier Remy
2003-09-10 7:10 Beck01, Wolfgang
2003-09-10 8:12 ` Fernando Alegre
2003-09-10 8:18 ` Jacques Garrigue
2003-09-10 10:39 ` skaller
2003-09-10 9:48 ` skaller
2003-09-10 11:34 ` Frederic De Jaeger
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