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Date: Wed, 24 Jul 1996 09:37:56 +0200
To: John Gerard Malecki <johnm@vlibs.com>
Cc: caml-list@pauillac.inria.fr
Subject: Label Names Space - philosophy or implementation?
In-Reply-To: <199607230040.RAA11401@owl.vlibs.com>
References: <199607230040.RAA11401@owl.vlibs.com>
Sender: weis


John Gerard Malecki writes:
> 
> A co-worker has (vehemently) pointed out to me that record label names
> cannot be shared.  For example, the following fails
> 
> 	type foo = { name : string; x : int }
> 	let    a = { name = "foo";  x = 1 }
> 
> 	type bar = { name : string; y : float }
> 	let    b = { name = "bar";  y = 9. }
> ...
> field with a standardized label.  This makes it easier for him to
> write printers for his data-structure.  Does anyone have a
> recommendation to make to him?

	type 'a foobar = { name : string; x : 'a}
	let print_name {name = s} = print_string s
	print_name { name = "foo"; x = 1 }
	print_name { name = "bar";  x = 9. }

or using classes and inheritance (I do not like it but ...) :

	class named (s:string) =
	  val private name = s
	  method name = name
	end
	class foo n (x:int) =
	  inherit named n
	  val private x = x
	  method x = x
	end
	class bar n (y:float) =
	  inherit named n
	  val private y = y
	  method y = y
	end
	let print_name x = print_string x#name
	print_name (new foo "foo" 1)
	print_name (new bar "bar" 9.)

My 0.02 euros...

--Pascal