Re: [Caml-list] Comparing variant types

[Gabriel Scherer <gabriel.scherer@gmail.com>]

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>
> You want to avoid code size quadratic in the number of constructors. Which
> is possible:
>


let cmp x y = match x, y with
> A, A -> true
> | A, _ | _, A -> false
> | B, B -> true
> | B, _ | _, B -> false


With one twist though: if done that way for (type foo = A | B), the last (_,
B) pattern is actually redundant. If you want to avoid getting a warning
here, you should comment it out or remove it:

  let cmp x y = match x, y with
  | A, A -> true
  | A, _ | _, A -> false
  | B, B -> true
  | B, _ (*| _, B*) -> false

That's the style I use.

On Sat, Apr 30, 2011 at 3:43 PM, craff73@gmail.com <craff73@gmail.com>wrote:

> Hello,
>
> You want to avoid code size quadratic in the number of constructors. Which
> is possible:
>
> let cmp x y = match x, y with
> A, A -> true
> | A, _ | _, A -> false
> | B, B -> true
> | B, _ | _, B -> false
> ...
>
> Cheers
> Christophe
>
> --
> Envoyé de mon téléphone Android avec K-9 Mail. Excusez la brièveté.
>
>

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