From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <maranget@yquem.inria.fr>
Received: by yquem.inria.fr (Postfix, from userid 18041)
	id E58AFBC57; Tue,  8 Jun 2010 11:36:51 +0200 (CEST)
Date: Tue, 8 Jun 2010 11:36:51 +0200
To: David Allsopp <dra-news@metastack.com>
Cc: 'bluestorm' <bluestorm.dylc@gmail.com>, caml-list@yquem.inria.fr,
	'W Dan Meyer' <wojciech.meyer@googlemail.com>
Subject: Re: [Caml-list] Converting variants with only constant constructors to integers
Message-ID: <20100608093651.GA8296@yquem.inria.fr>
References: <4C0D3557.1020200@gmail.com> <010d01cb0672$09f3eb90$1ddbc2b0$@romulus.metastack.com> <4C0D4C88.4070102@gmail.com> <AANLkTinsp9JgePfV6aZVyypOdjNHmNzz3E_i-U3Zvo9S@mail.gmail.com> <877hma78xf.fsf@gmail.com> <013a01cb06de$32c6d930$98548b90$@romulus.metastack.com> <AANLkTilku93HnpBpA6a3elkHX6u6lodPtPq7NFVKsV89@mail.gmail.com> <015201cb06ea$f06adc00$d1409400$@romulus.metastack.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <015201cb06ea$f06adc00$d1409400$@romulus.metastack.com>
User-Agent: Mutt/1.5.9i
From: maranget@yquem.inria.fr (Luc Maranget)
X-Spam: no; 0.00; variants:01 constructors:01 integers:01 maranget:01 maranget:01 compiler:01 hashtable:01 compiler:01 lookup':01 --luc:01 ocamlopt:01 -dlambda:01 compilation:01 compile:01 luc:01 

> Of course, if you have the following:
> 
> type t = A | B | C
> let int_of_t = function
>   A -> 0
> | B -> 1
> | C -> 2
> 
> Then in fact I believe that the compiler already converts that to a
> hashtable lookup instead of a sequence of jumps..

The compiler does not convert the above code to 'hashtable lookup'.


--Luc

PS>

To have a look at produced code.
* put your (Caml) code in some file say a.ml;
* compile as ocamlopt -S a.ml
* look at a.s

You can also use various options, such as -dlambda or -dcmm, to
see intermediate stages of the compilation process.