Re: [Caml-list] type matching

[skaller <skaller@users.sourceforge.net>]

On Sat, 2004-09-18 at 00:53, Flávio Leonardo Cavalcanti de Moura wrote:
> Hi there, 
> 
> I am trying to build a normalisation function for lambda terms which
> This expression has type exlambda * int * 'a list * string
> but is here used with type Setypes.exlambda * int * int list * string
> 
> My dout is: shouldn't the type exlambda match with the type
> Setypes.exlambda as well as 'a list with int list in the two last line
> above?
> 
> Why Ocaml differ between the types Setypes.exlambda and exlambda?

module type X = sig type t end
module Y = struct type t = int end

--> module Y : sig type t = int end


module Z : X = Y

--> module Z : X

let i : Y.t = 1

--> val x : Y.t = 1

let ni : Z.t = 1

--> This expression has type int but is here used with type Z.t

Y.t is just an alias for 'int'
However Z.t is an abstract type because X.t is.

-- 
John Skaller, mailto:skaller@users.sf.net
voice: 061-2-9660-0850, 
snail: PO BOX 401 Glebe NSW 2037 Australia
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