Re: [Caml-list] Forcing a Map type: setting the value type

[Hugo Ferreira <hmf@inescporto.pt>]

On 05/02/2011 03:11 PM, Çagdas Bozman wrote:
> I would use something like this :
>
> module IntMap = Map.Make (struct
>    type t = int
>    let compare = Pervasives.compare
> end);;
>
> # let m = IntMap.empty;;
> val m : 'a IntMap.t = <abstr>
> # let m = IntMap.add 1 42 m;;
> val m : int IntMap.t = <abstr>
> # IntMap.find 1 m ;;
> - : int = 42
>

Maybe I did not express myself correctly.
The above would also work with any other type for the
parameter 'a. I want only integers for it. So:

# let m = IntMap.empty;;
# let m = IntMap.add 1 "42" m;;

should not work.

R,
Hugo F.


> 2011/5/2 Hugo Ferreira <hmf@inescporto.pt <mailto:hmf@inescporto.pt>>
>
>     Hello,
>
>     I would like to make a Map with the key = int and
>     and the value also equal to int. Is this possible?
>     The example below does not work.
>
>     TIA,
>     Hugo F.
>
>
>     # module Domains : Map.S with type key = int
>                              with type (+'a) t = int = Map.Make( Int );;
>     Error: Signature mismatch:
>            Modules do not match:
>              sig
>                type key = Int.t
>                type 'a t = 'a Map.Make(Int).t
>                val empty : 'a t
>                val is_empty : 'a t -> bool
>                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
>                val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
>                val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
>              end
>            is not included in
>              sig
>                type key = int
>                type 'a t = int
>                val empty : 'a t
>                val is_empty : 'a t -> bool
>                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
>                val compare : ('a -> 'a -> int) -> 'a t -> 'a t -> int
>                val equal : ('a -> 'a -> bool) -> 'a t -> 'a t -> bool
>              end
>            Type declarations do not match:
>              type 'a t = 'a Map.Make(Int).t
>            is not included in
>              type 'a t = int
>
>
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>
>
> Best regards,
> --
> Çagdas Bozman <cagdas@bozman.fr <mailto:cagdas@bozman.fr>>
>