Re: [Caml-list] Modules and record fields

[Goswin von Brederlow <goswin-v-b@web.de>]

On Sun, May 25, 2014 at 05:02:46PM +0200, Gabriel Scherer wrote:
> When I write M.v.f, it is not always the case that the field f is
> exported by the module M. Consider for example:
> 
> module A = struct
>   type t = { f: int }
> end
> 
> module M = struct
>   open A
>   let v = { f = 1 }
>   type u = { f : string }
> end
> 
> print_int M.v.f
> 
> This rightly fails (with a warning) as one should write M.v.A.f to be
> fully precise about the scope. Note that M.v.M.f or M.(v.f) would have
> a completely different (and wrong) meaning.

Here is another example:

module V2 = struct
  type t = { x:int; y:int; }
  let make x y =  { x; y; }
end

module V3 = struct
  type t = { x:int; y:int; z:int; }
  let make x y z =  { x; y; z; }
  let of_v2 v = { x = v.V2.x; y = v.V2.y; V3.z = 0; }
  let to_v2 v = { V2.x = v.x; V2.y = v.y; }
end

let v3_of_v2 v = { V3.x = v.V2.x; V3.y = v.V2.y; V3.z = 0; }

MfG
	Goswin