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From: Steve Jones - JON <jon@hpodid2.eurocontrol.fr>
Subject: Re: p(x: out File_Type)
Date: 1996/12/03
Message-ID: <2su3q396xi.fsf@hpodid2.eurocontrol.fr>#1/1
X-Deja-AN: 202300713
references: <57u5ik$qdc$1@goanna.cs.rmit.edu.au>
organization: Eurocontrol Experimental Centre, Bretigny-Sur-Orge, France
newsgroups: comp.lang.ada
Date: 1996-12-03T00:00:00+00:00
List-Id: <comp.lang.ada>


ok@goanna.cs.rmit.edu.au (Richard A. O'Keefe) writes:

> 
> Does
> 
> 	procedure P(...; X: out File_Type)
> 
> ever make sense, where File_Type is one of the standard file types
> (from Sequential_IO, Direct_IO, or Text_IO)?
First place when this would be used is when it conflicts with
a company standards, some detail that functions should be non
destructive operators only.  So you could have a standard function like

procedure Initialise_Recording(Recording_Number   : in INTEGER;
                               Workstation_Number : in NATURAL;
                               Recording_File     : out File_Type);

(The actual names and types of the paramaters have been change to
protect the innocent).

I have seen single out parameters on other occasions, normally to
keep a standard interface (ie 15 procedures doing similar things
all implemented as procedures but 6 have an out parameter).

But the first reason is the one I see most often, to be fair to it
as a rule in standards it seemed to work fairly well on the last
project I was on as it made it clearer where people were doing the
actual work and what was information serving.

[snip]