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From: mheaney@ni.net (Matthew Heaney)
Subject: Re: Rules for Representation of Subtypes
Date: 1996/09/29
Message-ID: <mheaney-ya023180002909961026240001@news.ni.net>#1/1
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references: <dewar.843920516@schonberg> <DyGyFv.JA1@world.std.com>
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organization: Estormza Software
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newsgroups: comp.lang.ada
Date: 1996-09-29T00:00:00+00:00
List-Id: <comp.lang.ada>


In article <DyGyFv.JA1@world.std.com>, bobduff@world.std.com (Robert A
Duff) wrote:

>Anyway, are you saying that GNAT fails to optimize cases like this:
>
>    X: Integer range 1..10 := 1;
>    ...
>    if X < 10 then -- must be true
>
>But what if the "..." contains an unchecked conversion that sets X to
>11?

That's easy: program execution is erroneous.  Very likely the compiler
*will* make that optimization. s

If one leaves the language (via unchecked_conversion) and violates the type
constraints, then he the programmer is at fault.  Who can say what the
compiler does, because program behaviour is in fact undefined.

>- Bob

Matt

--------------------------------------------------------------------
Matthew Heaney
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(818) 985-1271