Re: [Caml-list] Pattern matching of records

[Nicolas Ojeda Bar <n.oje.bar@gmail.com>]

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Hi Leonardo,

You only need to fully qualify _one_ label in order to disambiguate the
record type, for example:

  match s0 with
  | {S.a = 0; b = 0} -> true
  | _ -> false

Cheers,
Nicolas


On Wed, Sep 16, 2015 at 2:19 PM, Leonardo Laguna Ruiz <modlfo@gmail.com>
wrote:

>
> I have the following type
>
> (* File: S.ml *)
> module S = struct
>    type s =
>       {
>          a : int;
>          b : int;
>       }
> end
>
>
> I I have found that for creating records I can do as follows:
>
> (* File: main.ml *)
> open S
> let s0 = S.{ a = 0; b = 0}
>
>
> However this does not work for pattern matching:
>
> (* this does not work *)
> match s0 with
> | S.{ a = 0 ; b = 0 } -> true
> | _ -> false
>
>
> These two alternatives work, but one with a warning and the other
> (depending on the type) is too verbose:
>
> (* this produces a warning *)
> match s0 with
> | { a = 0 ; b = 0 } -> true
> | _ -> false
>
> (* this works *)
> match s0 with
> | { S.a = 0 ; S.b = 0 } -> true
> | _ -> false
>
>
> Is there any other way of writing pattern matches as compact as S.{ a = 0
> ; b = 0 } ? (which is consistent to the construction of the same value)
>
> I know that it's possible to do:
>
> let open S in
> match s0 with
> | { a = 0 ; b = 0 } -> true
> | _ -> false
>
> but the main reason I don't do it is because I have more records like:
>
> match s0,k0 with
> | { S.a = 0 }, {K.a = 0 } -> true
>
>
>
> Best regards,
>
> Leonardo
>
>
>
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