Re: Fixed point constants issue

["Vinzent Hoefler" <nntp-2010-09@t-domaingrabbing.de>]

On Fri, 24 Sep 2010 16:43:29 +0200, Markus Schöpflin <no@spam.spam> wrote:

>     TEN_FEET_1 : constant          := HEIGHT * FEET_PER_METER;
>     TEN_FEET_2 : constant ALTITUDE := HEIGHT * FEET_PER_METER;
> begin
>     ALTITUDE_IO.PUT (TEN_FEET_1); NEW_LINE; -- gives 3.0
>     ALTITUDE_IO.PUT (TEN_FEET_2); NEW_LINE; -- gives 5.0 (*)
> end FIXED_POINT;
> --->%---
>
> (*) This certainly looks like FEET_PER_METER is converted to ALTITUDE  
> before doing the multiplication.

Now that's interesting. Let me re-iterate: We have an Ada95 compiler  
behaving
as expected (although not necessarily intuitive) (GNAT), an Ada95 compiler
behaving like what's supposed to be an Ada83 difference (GreenHills, to
finally reveal the name), and now an Ada83 compiler behaving as if it were
an Ada95 compiler.

At least according to what I understood so far... seriously, I'm no less
confused than I was before.

> Another question regarding the implicit conversion from universal_real  
> to ALTITUDE: Does ARM83-3.5.6 apply here? And what does this mean: "If  
> the universal_real value is a safe number, the implicit conversion  
> delivers the corresponding value; if it belongs to the range of safe  
> numbers but is not a safe number, then the converted value can be any  
> value within the range defined by the safe numbers next above and below  
> the universal_real value." Is the compiler free to convert  
> FEET_PER_METER to either 0.0 or 0.5?

This would by my understanding, Ada95 puts it in different terms, but
basically the compiler seems to be allowed to choose any of both choices.

But IANALL (although today a call from my co-worker started with
"Ada Support there?" *g*).


Vinzent.

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