Re: [Caml-list] syntax of private constructors in CVS version

[Shaddin Doghmi <shaddin@mitre.org>]

brogoff@speakeasy.net wrote:

>On Fri, 27 Jun 2003, Shaddin Doghmi wrote:
>  
>
>> From the CVS version  changes file, under language features:
>>
>>- Support for "private types", or more exactly concrete data types
>>  with private constructors or labels.  These data types can be
>>  de-structured normally in pattern matchings, but values of these
>>  types cannot be constructed directly outside of their defining module.
>>
>>What is the syntax for those? is there some kind of documentation on the 
>>CVS server, like a development version of the manual or something?
>>    
>>
>
>No documents are available yet. Check out the following:
>
>bpr@granite[bpr]$ ledit ~/bin/ocaml
>        Objective Caml version 3.06+36 (2003-06-19)
>
># type t = private { x : int; y : int } ;;
>type t = private { x : int; y : int; }
># type ('a, 'b) choice = private L of 'a | R of 'b;;
>type ('a, 'b) choice = private L of 'a | R of 'b
># let p0 = { x = 0; y = 0 } ;;
>One cannot create values of the private type t
># module Point2D : 
>    sig 
>      type t = private { x : int; y : int }
>      val grid : int 
>      val mkPoint : int -> int -> t 
>    end = 
>  struct
>    type t = { x : int; y : int }
>    let grid = 10 
>
>    let snap i =
>      let rem = i mod grid in
>      if rem <= 0 then
>	i - rem
>      else
>	i - rem + grid
>
>    let mkPoint x y = { x = snap x; y = snap y } 
>  end;;
>module Point2D :
>  sig
>    type t = private { x : int; y : int; }
>    val grid : int
>    val mkPoint : int -> int -> t
>  end
># open Point2D;;
># match mkPoint 5 5 with { x = x; y = y } -> Printf.printf "(%d, %d)\n" x y;;
>(10, 10)
>- : unit = ()
>
>-- Brian
>
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>  
>
neat. However, private doesnt seem to work with polymorphic 
variants(tried a bunch of variations of the syntax, nothing worked). 
Looking at the parser source seems to confirm that (i think ?), or am i 
missing something....




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