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From: "J-P. Rosen" <rosen@adalog.fr>
Newsgroups: comp.lang.ada
Subject: Re: Fixed point constants issue
Date: Tue, 14 Sep 2010 08:54:20 +0200
Organization: Adalog
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Date: 2010-09-14T08:54:20+02:00
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Le 13/09/2010 23:08, Vinzent Hoefler a écrit :
>>> And, obviously it does this that when evaluating
>>>
>>>    TEN_FEET_4 : constant Altitude := Altitude (HEIGHT * FEET_PER_METER);
>>
>> Well, it does not, because here another type is involved.
> 
> Yes. So, the expression HEIGHT * FEET_PER_METER in the one case is
> evaluated by using the result type's multiplication operator and if the
> conversion is present, it is not, giving the more precise result.
> 
> That's still a bit crazy, IMHO.
> 
Every language with overloading has to decide whether resolution goes
from the outside to the inside, or the other way round. In the case of
Ada, it is the "enclosing context" that determines the type of what's in
it. If the enclosing context is a type conversion, it tells nothing
about the expected type of its argument, hence the fall back to
universal types. If the enclosing context is typed, it determines the
type of the "*" operator.
-- 
---------------------------------------------------------
           J-P. Rosen (rosen@adalog.fr)
Visit Adalog's web site at http://www.adalog.fr