Re: [Caml-list] Subtyping (or something like it)

[octachron <octa@polychoron.fr>]

With OCaml 4.06, if what you really want is to have a nice syntax for 
array indexing, one solution would be to define your own indexing operators:

   let (  .%{ } ) a k = a.{k}
   let ( .%{ } <- ) a k x = a.{k} <- x

These operators can be used like standard indexing operators

     let x = a.%{ 0 } in
     a.%{ 1 } <- x

and exported with

    val (  .%{ } ): …
    val ( .%{ } <- ): …

Nevertheless, contrarily to Bigarray, there is no implicit conversion 
for multidimensional array,
in other words

     a .%{0,1}

will not work out of the box.

However, if needed, it is possible to use qualified indexing operators 
to circumvent this difficulty:

   module D1 = struct let ( .%{} ) a k = a.{k} end
   module D2 = struct let ( .%{} ) a (k,l) = a.{k,l} end
   let x_ij = mat.D2.%{i, j}
   let x_0 = vector.D1.%{0}

See also the manual for more details: 
http://caml.inria.fr/pub/docs/manual-ocaml/extn.html#s%3Aindex-operators .

− octachron.