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From: Xavier Leroy <xavier.leroy@inria.fr>
To: Alessandro Baretta <alex@baretta.com>
Cc: Ocaml <caml-list@inria.fr>
Subject: Re: [Caml-list] Has laziness changed type?
Date: Mon, 9 Sep 2002 16:23:20 +0200	[thread overview]
Message-ID: <20020909162320.D1781@pauillac.inria.fr> (raw)
In-Reply-To: <3D7A7C8B.9070901@baretta.com>; from alex@baretta.com on Sun, Sep 08, 2002 at 12:24:11AM +0200

> I think I recall Lazy.t being defined in 3.04 as = Value of 
> ... | Exception of ... | Suspension of ...
> or something of the sort. Now Lazy.t is defined simply as 
> lazy_t. But what *is* lazy_t exactly?

An abstract type.  You don't want to know :-)  More seriously: in
3.06, the compiler and runtime system represent lazy values more
efficiently; in particular, the "Value of" indirections present in
3.04 are now shortened by the GC whenever possible.  As a consequence,
the representation of lazy values no longer matches that of a Caml datatype.

> Can I apply pattern-matching on it?

No.  The general "contract" of a lazy value is that you should never
have to distinguish whether it's been evaluated already or not.  Just
perform Lazy.force on the lazy value and match on the result.

- Xavier Leroy
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  reply	other threads:[~2002-09-09 14:23 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-09-07 22:24 Alessandro Baretta
2002-09-09 14:23 ` Xavier Leroy [this message]
2002-09-09 14:59   ` Alessandro Baretta
2002-09-09 15:00     ` John Prevost
2002-09-09 15:25       ` [Caml-list] Has laziness changed type? (with a plea to Xavier...) Alessandro Baretta

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