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From: mg@asp.camb.inmet.com (Mitch Gart)
Subject: "use" clauses and Ada 95 OOP
Date: 1996/07/17
Message-ID: <Dup54L.2q2.0.-s@inmet.camb.inmet.com>#1/1
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newsgroups: comp.lang.ada
Date: 1996-07-17T00:00:00+00:00
List-Id: <comp.lang.ada>


In Ada 95 OOP we can have the situation where a call

    pkg1.func(x)

dispatches at runtime to

    pkg2.func(x)

because x is a classwide tagged type whose base type is in pkg1 but whose 
runtime tag says it's in fact a derived type in pkg2.

It seems to me that this notation is misleading because a reader might
think that the function in pkg1 will be executed.  

Therefore with tagged types I have adopted the style of always using
"use" clauses and writing the call

    func(x);

in the source code.  This seems less misleading to me.  I never used to
use "use" clauses in Ada 83 but I now use them a lot in Ada 95 when 
calling dispatching operations.

Have other people adopted this style?  Comments?  People who have written
coding standards which say "don't use 'use' clauses", do you think this
rule is still a good idea with Ada 95 dispatching?

To me the C++/Java syntax

    x.func

seems clearer than the Ada syntax in this case because what is being
called is the function that is associated with X at runtime, rather than
the function that comes from a given package.

-- Mitch Gart 
-- mg@inmet.com