Le 27 oct. 09 à 19:24, Jake Donham a écrit :
On Tue, Oct 27, 2009 at 3:28 AM, Marc de Falco <m...@de-falco.fr>
wrote:
The following code :
type 'a p = R of 'a t | E of float
and 'a t = { mutable p : 'a p; c : 'a }
let f =
let x = sqrt(2.0) in
fun () -> { c = `A; p = E 0.0 }
generates the error :
The type of this expression, unit -> _[> `A ] t,
contains type variables that cannot be generalized
but if I change the x definition to "let x = 2.0 in" then it works.
I think this is just the value restriction. The type of f is
generalized only if the right hand side is a value (rather than an
expression needing some computation); in your examples the one that
fails is not a value, the others are. It looks like there is a
relaxation to allow let bindings which are themselves values.
With the -dlambda option, the "sqrt(2.0)" version gives:
(let
(f/92
(let (x/93 (caml_sqrt_float 2.0))
(function param/94 (makemutable 0 [1: 0.0] 65a))))
whereas the "2.0" version gives:
(let (f/96 (let (x/97 2.0) (function param/98 (makemutable 0 [1:
0.0] 65a))))
i.e. this last version is inlined.
I thought the yping was done before (??)
V.
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