RE: [Caml-list] Basic question about modules

RE: [Caml-list] Basic question about modules

[Tim Docker]

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> Well, you can use `ocamlc -i' to initially create the .mli file,
> or inspect its output for help.

Thanks - this is good. Looking at the output, I see that the entire
signature for the string map is present:

 | module StringMap :
 |   sig
 |     type key = String.t
 |     and 'a t = 'a Map.Make(String).t
 |     val empty : 'a t
 |     val add : key -> 'a -> 'a t -> 'a t
 |     val find : key -> 'a t -> 'a
 |     val remove : key -> 'a t -> 'a t
 |     val mem : key -> 'a t -> bool
 |     val iter : (key -> 'a -> unit) -> 'a t -> unit
 |     val map : ('a -> 'b) -> 'a t -> 'b t
 |     val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t
 |     val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
 |   end
 | type info = int list StringMap.t
 | and named_values = { details : info; }

Do I actually have to duplicate the above signature for the StringMap
as shown above in my own mli file (and other similar types).
This seems pretty heavy handed.

At the end of the day I am just attempting to define some datatypes
that include maps of various types created with the Map.Make functor.

Thanks,

Tim


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Re: [Caml-list] Basic question about modules

[Kenneth Knowles]

> Do I actually have to duplicate the above signature for the StringMap
> as shown above in my own mli file (and other similar types).
> This seems pretty heavy handed.

No, as I said you can do this (I just looked it up, but haven't tested):

module StringMap : Map.S with type key = string

Kenn

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Re: [Caml-list] Basic question about modules

[Matthieu Dubuget]

>
> If I want to restrict what gets exported, I have to
> write an x.mli file. Whilst I've written mli files for simple
> types and functions, I'm at a loss as how to write the contents
> of the mli file that corresponds to the one automatically generated
> above (specifically the StringMap bit).
>
When you are ready with your module, the simplest way is to generate the 
mli file with
ocamlc -i x.ml > x.mli
and then edit x.mli to restrict the exported parts.

I hope I understood your question and that this will help.

Salutations

Matthieu Dubuget

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Re: [Caml-list] Basic question about modules

[Kenneth Knowles]

> types and functions, I'm at a loss as how to write the contents
> of the mli file that corresponds to the one automatically generated
> above (specifically the StringMap bit).
> 
> A pointer would be much appreciated, either how to write the .mli
> file, or a generally better way of doing this stuff.

Well, you can use `ocamlc -i' to initially create the .mli file, or inspect its
output for help.  Also, by typing it into the ocaml toplevel you get:

# module StringMap = Map.Make(String);;
module StringMap :
  sig
    type key = String.t
    and 'a t = 'a Map.Make(String).t
    val empty : 'a t
    val add : key -> 'a -> 'a t -> 'a t
    val find : key -> 'a t -> 'a
    val remove : key -> 'a t -> 'a t
    val mem : key -> 'a t -> bool
    val iter : (key -> 'a -> unit) -> 'a t -> unit
    val map : ('a -> 'b) -> 'a t -> 'b t
    val mapi : (key -> 'a -> 'b) -> 'a t -> 'b t
    val fold : (key -> 'a -> 'b -> 'b) -> 'a t -> 'b -> 'b
  end

There is some syntax for "Map.S with type key = String.t" that would be a bit
prettier, but I don't remember it offhand.

Kenn

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[Caml-list] Basic question about modules

[Tim Docker]

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Having used haskell, I'm getting to grips with the core ocaml
language, but am somewhat confused by modules.

If I compile a simple file, X.ml:

 | module StringMap = Map.Make (String)
 | 
 | type info = int list StringMap.t
 |
 | type named_values = {
 |    details : info
 | }
 |
 | ..... other stuff ....

then ocamlc will automatically build a x.cmi file that exports
everything. I can use this from another file Y.ml:

 | let x = X.StringMap.empty;;
 |
 | let y = { X.details=X.StringMap.add "xxx" [1;2;3] x }

although the X.StringMap.fn syntax seems a bit unwieldy.

If I want to restrict what gets exported, I have to
write an x.mli file. Whilst I've written mli files for simple
types and functions, I'm at a loss as how to write the contents
of the mli file that corresponds to the one automatically generated
above (specifically the StringMap bit).

A pointer would be much appreciated, either how to write the .mli
file, or a generally better way of doing this stuff.

Thanks,

Tim


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