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From: stdsee01@pip.shsu.edu (Road Pilot)
Newsgroups: comp.lang.ada
Subject: Re: Syntax question
Date: 11 Mar 1995 15:44:14 -0600
Organization: Sam Houston State University
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Date: 1995-03-11T15:44:14-06:00
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Geoffrey Hollingworth (etlghh@garbo.ericsson.se) wrote:
: Hi
: 
: I am currently researching into real time languages and hope
: you ada experts can explain something to me.  I apologise for
: my lack of knowledge in ada.
: When binding formal parameters with actual parameters the '=>'
: operator is used, irrespective of whether the formal parameter
: is declared as IN, INOUT or OUT.  Is there a reason for this ?
: If I proposed an alternative syntax where "=>" indicated the FP
: was an IN parameter, "<=" to indicate an OUT parameter and "<=>"
: to indicate an INOUT.
: Then the caller of the procedure/function would have explicitly
: had to understand to direction of the parameters and at the same
: time increased the readability of his/her code.
: Is there a fundamental flaw in this line of thinking ?
: Does ada manage this problem via a different mechanism ?
: 
: Any information, historical or otherwise, would be a great help
: to me and greatly appreciated.
: 
: thanks
: 
: /geoff

Well, the arrow symbol "=>" is not meant to imply direction.  It is used in
the case statement (ex: WHEN choice => statement) and in aggregate assingments
as well (ex: initializing specific cells of an array without multiple index
references).  This is all in contrast to positional reference.  In your a
function/procedure call, the use of the arrow notation is completely
optional.  In some cases of multiple parameters, it makes it easier to keep
them straight.  I like to use them mainly because it avoids confusion.

Like so:
procedure insert( list : in out integer; item : in integer ) is

	insert( 2, 4 );   OR  insert (list=>2, item=>4);

 either way will work. 
 
I don't know if this helps any or just confuses more, but I guess the main
thing is that the arrow is more like a placeholder or referencing tool and
is not meant to imply direction.

Sloaner
stdsee01@pip.shsu.edu