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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Running a preprocessor from GPS?
Date: Thu, 30 Jul 2015 13:16:46 -0500
Organization: Jacob Sparre Andersen Research & Innovation
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Xref: news.eternal-september.org comp.lang.ada:27230
Date: 2015-07-30T13:16:46-05:00
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"Jeffrey R. Carter" <spam.jrcarter.not@spam.not.acm.org> wrote in message 
news:mpbbq4$nkm$1@dont-email.me...
...
> One of the few arguments I've heard for conditional expressions that might 
> make
> sense is that
>
> X := (if Y then 2 else 0);
>
> makes it clear that the purpose of the "if" is to choose the value of X, 
> while in

Yes, I suppose that's true. (It doesn't come up that often in practice, as 
usually there is something else in one of the branches, like a trace or a 
second assignment.)

The main reason I suggest using them is if the expression needs to be 
static:

   X : constant Integer := (if Y then 2 else 0);

If Y is static, then this expression will be static. In previous versions of 
Ada, one had to use tricky expressions involving multiplying by the 
Boolean'Pos to get a static expression, at huge readability cost.

And, of course, if an expression is required for other reasons 
(Preconditions, Predicates, expression functions), then you have no choice. 
Introducing a function (and coming up with a meaningful name for it!!) is a 
pain and does not necessarily help the readability of these things (and it 
definitely reduces the possibilities for proof/optimization at compile-time 
[as opposed to in a separate, whole program tool like SPARK]).

                                         Randy.