Re: [Caml-list] checking for same ctor type?

[Brian Rogoff <bpr@best.com>]

On Wed, 27 Jun 2001, Chris Hecker wrote:
> What's the right way to check if two variants have the same ctor, but
> not necessarily the same values in the ctor parms?
> 
> For example, I want to check if both data_types are Strings:
> 
> type data_type =
>     String of string
>   | Float of float
> 
> let a = String "foo"
> let b = String "bar"
> let c = Float 2.0
> 
> let ctor_equal a b = ???

let ctor_equal a b = 
  match a,b with 
  String(_),String(_) | Float(_),Float(_) -> true | _,_ -> false

> ctor_equal a b = true
> ctor_equal a c = false
> 
> I can think of a couple definitions of ctor_equal, one using
> Hashtbl.hash_param 1 1 and one using Obj.tag (which both appear to be
> doing the same thing).  Both of these seem a bit cheesy and
> implementation dependent.

Yes, but there's only one implementation, right? 

> Is there a better way?

Beauty is in the eye of the beholder. 

-- Brian


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