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From: "Smark" <not.provided@all.com>
Newsgroups: comp.lang.ada
Subject: Default expression only allowed for "in" parameters - why?
Date: Fri, 6 Apr 2001 15:41:52 -0500
Organization: Lockheed Martin Corporation
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Date: 2001-04-06T15:41:52-05:00
List-Id: <comp.lang.ada>

LRM 6.1(19):
    A default_expression is only allowed in a parameter_specification
    for a formal parameter of mode in.

I recently had a situation in which it was desirable for me to have
a default value for an "out" parameter of a function.  It was something
like:

procedure Do_Something (Data   : in Some_Type;
                        Status : out Status_Type);

Normally, Status = Ok.  It seemed to me that, rather than setting
Status := Ok at the beginning of my procedure, it would make sense to
just set the default value in the procedure spec.  That is:

procedure Do_Something (Data   : in Some_Type;
                        Status : out Status_Type := Ok);

It also seemed like a strange idea, because I never recalled seeing
it done.  Sure enough, it is prohibited by the LRM.  What is the
rationale for this?

TIA,
Mark