[Caml-list] variant type

[Caml-list] variant type

[Ye Wu]

Could you please tell me why the following doesn't work?

type shape = Square of int * int * int
        |Circle of float * float * float;;
let area s =
  match s with
    Square (_, _, d) -> d * d
   |Circle (_, _, r) -> 3.14 *. r *. r;;

Regards,
Ye


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Re: [Caml-list] variant type

[Owen Gunden]

On Tue, Jun 17, 2003 at 02:03:35PM -0400, Ye Wu wrote:
> Could you please tell me why the following doesn't work?

Sure.

> type shape = Square of int * int * int
>        |Circle of float * float * float;;
> let area s =
>  match s with
>    Square (_, _, d) -> d * d
>   |Circle (_, _, r) -> 3.14 *. r *. r;;

It's because the area function is not well-typed.  If the area function is
operating on a Square it wants to return an int; if it's operating on a
Circle it wants to return a float.  It can only return one type.

Owen

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RE: [Caml-list] variant type

[Alex Romadinoff]

Hi

Just think what is the type of your function?
shape -> int or shape -> float ????

Regards,
Alex

-----Original Message-----
From: owner-caml-list@pauillac.inria.fr
[mailto:owner-caml-list@pauillac.inria.fr] On Behalf Of Ye Wu
Sent: Tuesday, June 17, 2003 10:04 PM
To: caml-list@inria.fr
Subject: [Caml-list] variant type

Could you please tell me why the following doesn't work?

type shape = Square of int * int * int
        |Circle of float * float * float;;
let area s =
  match s with
    Square (_, _, d) -> d * d
   |Circle (_, _, r) -> 3.14 *. r *. r;;

Regards,
Ye


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http://caml.inria.fr
Bug reports: http://caml.inria.fr/bin/caml-bugs FAQ:
http://caml.inria.fr/FAQ/
Beginner's list: http://groups.yahoo.com/group/ocaml_beginners

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