From: pascal.obry@der.edfgdf.fr (Pascal Obry)
Subject: Re: Is 'out' different from 'in out' (Was: Uninitialized "out" parameters)
Date: 1996/07/24
Date: 1996-07-24T00:00:00+00:00 [thread overview]
Message-ID: <4t55jl$e4o@cf01> (raw)
In-Reply-To: gauthier-2307961037570001@164.81.60.62
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gauthier@unilim.fr (Michel Gauthier) wrote:
>They all confirm what I was not entirely sure to understand correctly.
>There is no essential difference between 'out' and 'in out' parameters,
>and it is probably worth considering them to be the same thing.
>IMHO, it was a mistake of the 9X design. It's too late to repair.
>Possible useful style rule : avoid 'out' parameters, since they
>are error-prone, and prefer 'in out'.
This is certainly true for the designer of the procedure. But 'out'
and 'in out' parameter provide one usefull information for the
caller of the procedure/function.
There is two parts in the programming job. You are sometimes designer
(you are fulfilling a demand - providing a functionality) and
sometimes client (using what has already be done). In our case 'out'
and 'in out' are differents for clients :
'out'
you don't have to initialize the parameter. this is done
inside the procedure/function.
'in out'
you have to initialize the paramter because the value passed to
the procedure/function will be used.
For example :
package P is
type T is limited private;
procedure Init1 (Item : in out T);
procedure Init2 (Item : out T);
end P;
I really prefer Init2 and I found Init1 misleading (how can I pass
an initialized parameter ?). So I don't found the rule 'avoid out
parameter' a good one.
Pascal.
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next prev parent reply other threads:[~1996-07-24 0:00 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
1996-07-18 0:00 Uninitialized "out" parameters Paul Whittington
1996-07-18 0:00 ` Adam Beneschan
1996-07-18 0:00 ` Robert Dewar
1996-07-19 0:00 ` Samuel Tardieu
1996-07-19 0:00 ` John Herro
1996-07-19 0:00 ` Tucker Taft
1996-07-23 0:00 ` Peter Hermann
1996-07-23 0:00 ` Robert A Duff
1996-07-19 0:00 ` Dale Stanbrough
1996-07-19 0:00 ` Adam Beneschan
1996-07-19 0:00 ` James A. Squire
1996-07-19 0:00 ` Adam Beneschan
1996-07-20 0:00 ` Michael Feldman
1996-07-21 0:00 ` Fergus Henderson
1996-07-21 0:00 ` Michael Feldman
1996-07-21 0:00 ` Robert Dewar
1996-07-22 0:00 ` Fergus Henderson
1996-07-23 0:00 ` Michael Feldman
1996-07-23 0:00 ` Robert Dewar
1996-07-25 0:00 ` Fergus Henderson
1996-07-24 0:00 ` Robert A Duff
1996-07-25 0:00 ` Richard A. O'Keefe
1996-07-24 0:00 ` Fergus Henderson
1996-07-19 0:00 ` Pascal Obry
1996-07-19 0:00 ` Peter Hermann
1996-07-18 0:00 ` Robert Dewar
1996-07-19 0:00 ` Peter Amey
1996-07-20 0:00 ` Fergus Henderson
1996-07-20 0:00 ` Robert Dewar
1996-07-21 0:00 ` Fergus Henderson
1996-07-21 0:00 ` Robert Dewar
1996-07-23 0:00 ` Fergus Henderson
1996-07-23 0:00 ` Robert A Duff
1996-07-24 0:00 ` Fergus Henderson
1996-07-24 0:00 ` Fergus Henderson
1996-07-23 0:00 ` Richard A. O'Keefe
1996-07-23 0:00 ` Robert A Duff
1996-07-24 0:00 ` Richard A. O'Keefe
1996-07-24 0:00 ` Robert A Duff
1996-07-25 0:00 ` Richard A. O'Keefe
1996-07-25 0:00 ` Robert A Duff
1996-07-24 0:00 ` Theodore E. Dennison
1996-07-25 0:00 ` Frank Manning
1996-07-25 0:00 ` Richard A. O'Keefe
1996-07-26 0:00 ` Frank Manning
1996-07-23 0:00 ` Robert Dewar
1996-07-24 0:00 ` Robert A Duff
1996-07-24 0:00 ` Fergus Henderson
1996-07-24 0:00 ` Fergus Henderson
1996-07-25 0:00 ` Richard A. O'Keefe
1996-07-25 0:00 ` Robert A Duff
1996-07-19 0:00 ` Peter Amey
1996-07-19 0:00 ` Michel Gauthier
1996-07-21 0:00 ` Robert A Duff
1996-07-21 0:00 ` Robert A Duff
1996-07-22 0:00 ` Is 'out' different from 'in out' (Was: Uninitialized "out" parameters) Michel Gauthier
1996-07-22 0:00 ` Tucker Taft
1996-07-22 0:00 ` Robert A Duff
1996-07-22 0:00 ` Robert Dewar
1996-07-23 0:00 ` Michel Gauthier
1996-07-23 0:00 ` Robert Dewar
1996-07-24 0:00 ` Pascal Obry [this message]
1996-07-25 0:00 ` Tucker Taft
1996-07-23 0:00 ` Uninitialized "out" parameters John Herro
1996-07-23 0:00 ` Robert A Duff
1996-07-24 0:00 ` Uninitialized variables, Java example Arra Avakian
1996-07-25 0:00 ` Robert A Duff
1996-07-25 0:00 ` Richard A. O'Keefe
1996-07-25 0:00 ` Robert A Duff
1996-07-23 0:00 ` Uninitialized "out" parameters Robert Dewar
1996-07-24 0:00 ` Peter Hermann
1996-07-26 0:00 ` Stephen J Bevan
1996-07-26 0:00 ` Robert A Duff
1996-07-24 0:00 ` Uninitialized variables, Java example Felaco
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