Re: [Caml-list] selecting GADT parameter

["Runhang Li" <marklrh@gmail.com>]

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Hi, 




I don’t think it is possible. 




Suppose you can use only one type constructor. What should be the type of function “fun a b -> Foo (a, b)”?


Kindly,




Runhang

On Fri, Jul 31, 2015 at 3:18 PM, Ashish Agarwal <agarwal1975@gmail.com>
wrote:

> You essentially still have 2 constructors, so this isn't quite what I'm
> aiming for.
> On Fri, Jul 31, 2015 at 9:57 AM, Carl Eastlund <ceastlund@janestreet.com>
> wrote:
>> Perhaps like this?  (Caveat: I typed this straight into gmail, I haven't
>> tried to compile or run this code at all.)
>>
>> type ('a, 'b, 'c) tag =
>> | Tag1 : ('a, int, int) tag
>> | Tag2 : ('a, string, 'a) tag
>>
>> type 'a t =
>> | Foo : ('a, 'b, 'c) tag * 'a * 'b -> 'c t
>>
>> On Fri, Jul 31, 2015 at 9:48 AM, Ashish Agarwal <agarwal1975@gmail.com>
>> wrote:
>>
>>> I have:
>>>
>>> type _ t =
>>> | Foo1 : 'a * int -> int t
>>> | Foo2 : 'a * string -> 'a t
>>>
>>> but I really want to merge these two cases. I want the return type to be
>>> based on the second arg when the second arg is int, and be based on the
>>> first arg otherwise. Any way to accomplish that?
>>>
>>>
>>
>>
>> --
>> Carl Eastlund
>>
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