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Date: Tue, 11 Dec 2001 22:48:22 +0100 (MET)
From: Alain Frisch <frisch@clipper.ens.fr>
To: Xavier Leroy <xavier.leroy@inria.fr>
cc: Willem Duminy <WDuminy@mweb.com>,
        "Caml-List (E-mail)" <caml-list@inria.fr>
Subject: Re: [Caml-list] Pairs vs. Records
In-Reply-To: <20011211220928.C30744@pauillac.inria.fr>
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On Tue, 11 Dec 2001, Xavier Leroy wrote:

> > I had a progarm that used pairs int*int as the basis of the primary data
> > structure.  After changing it to use records {row:int;col:int} the
> > program runs slower.
>
> This is very surprising indeed, because the OCaml compilers generate
> *exactly the same code* for building/accessing tuples and for
> building/accessing records (with no mutable fields).

I guess you know this better than I ;) but one can observe difference in
generated code with pattern matching:

# fun x y -> match (x,y) with (a,b) -> a + b;;
        closure L1, 0
        return 1
        restart
L1:     grab 1
        acc 1
        push
        acc 1
        addint
        return 2

- : int -> int -> int = <fun>
# fun x y -> match {row=x;col=y} with {row=a;col=b} -> a + b;;
        closure L1, 0
        return 1
        restart
L1:     grab 1
        acc 1
        push
        acc 1
        makeblock 2, 0
        push
        acc 0
        getfield 1
        push
        acc 1
        getfield 0
        addint
        return 3


Of course, it would be surprising to find this kind of code with
records in a real program ...


-- 
  Alain

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