Re: [Caml-list] beginner question about pattern matching

["Matej Košík" <mail@matej-kosik.net>]

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On 10/19/2017 04:16 PM, vrotaru.md@gmail.com wrote:
> [ Rtag (_,_,_,_) as rtag] -> rtag

That is certainly possible.
It is equivalent to:

  | [rtag] -> rtag

but that's not what I am trying to do.  :-/

Instead of the whole

  Rtag (something1, something2, something3, something4)

I would like to bind just the 4-tuple
(without the Rtag label).

> 
> 
> On Thu, Oct 19, 2017, 16:39 Matej Košík <mail@matej-kosik.net <mailto:mail@matej-kosik.net>> wrote:
> 
>     Hi,
> 
>     I am trying to do simple pattern matching of these values:
>     https://github.com/ocaml/ocaml/blob/trunk/parsing/parsetree.mli#L145
> 
>     What I would like to do is:
> 
>        | [Rtag the_whole_4_tuple] ->
>            the_whole_4_tuple
> 
>     However, when I try to do that, I am getting:
> 
>       Error: The constructor Rtag expects 4 argument(s),
>              but is applied here to 1 argument(s)
> 
>     This:
> 
>         | [Rtag (f1,f2,f3,f4)] ->
>             f1,f2,f3,f4
> 
>     of course works but (regardless of the chosen bound variable names), it looks amateurish.
> 
>     What's the right way to do this?
>     (I would like just to bind a 4-tuple and then return it)
> 
>     (Apologies in advance for a stupid question.)
> 


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