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From: Samuel Mize <smize@imagin.net>
Subject: Re: Alternate to Unchecked_Conversion - Portable?
Date: 1999/02/23
Message-ID: <7av5h3$62g@news3.newsguy.com>#1/1
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References: <36d05e39.0@news.pacifier.com>
 <36d2638e.6427631@nntp.concentric.net> <m3sobxfpwd.fsf@mheaney.ni.net>
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Newsgroups: comp.lang.ada
Date: 1999-02-23T00:00:00+00:00
List-Id: <comp.lang.ada>

Matthew Heaney <matthew_heaney@acm.org> wrote:
> A copy doesn't necessarily occur.  If I use a constant declaration:
> 
> procedure Op (O : T) is
> 
>   OO : constant TT := UC (O);
> begin
> 
> 
> then (I assume) there isn't any copy of the source object.

This is an example of where the Ada programmer expects the
compiler to do intelligent things.  On the other hand, programmers
accustomed to other languages see a function call, and by golly they
expect there to be a function call!

This is one source of the erroneous "common wisdom" that Ada is
inherently slow.

I've had people argue against creating new subtypes because they
don't want to incur the run-time overhead of the type conversion:

       type New_Int is new Integer;
       Freem: Integer := Get_Value;
       New_Freem: New_Int;
    begin

       New_Freem := New_Int (Freem);
       -- Oh no!  It looks like a function call, so it must have
       -- the same run-time overhead as a function call!

Best,
Sam Mize

-- 
Samuel Mize -- smize@imagin.net (home email) -- Team Ada
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