From: Andrej Bauer <Andrej.Bauer@andrej.com>
To: Angela Zhu <angela22.zhu@gmail.com>,
caml-list <caml-list@yquem.inria.fr>
Subject: Re: [Caml-list] Ocaml type with constraints?
Date: Mon, 22 Sep 2008 00:05:18 +0200 [thread overview]
Message-ID: <48D6C51E.5060901@andrej.com> (raw)
In-Reply-To: <f82e818a0809211501x824e457y164c71c9ebc45a1d@mail.gmail.com>
Angela Zhu wrote:
> Hi,
>
> I want to define an OCaml type with constraints.
> For example:
>
> type item = Item of int * float;;
>
> If here this float type is for price of some item, and I want to make sure
> it is positive. In other words, if x = (xi, xf) of type item,
> I want to enforce, xf must >= 0.
>
> Is there a way to define OCaml type like this?
No, because Ocaml type checker always check all the types at compile
time. It is an undecidable problem whether a given expression of type
float evaluates to a non-negative number.
Best regards,
Andrej
next prev parent reply other threads:[~2008-09-21 22:05 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-21 22:01 Angela Zhu
2008-09-21 22:05 ` Andrej Bauer [this message]
2008-09-21 23:10 ` [Caml-list] " Martin Jambon
2008-09-21 22:50 ` Gordon Henriksen
2008-09-21 23:55 ` Jacques Garrigue
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