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From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Re: How to get Ada to ?cross the chasm??
Date: Wed, 2 May 2018 16:36:56 +0200
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Xref: reader02.eternal-september.org comp.lang.ada:51917
Date: 2018-05-02T16:36:56+02:00
List-Id: <comp.lang.ada>

On 02/05/2018 16:23, Paul Rubin wrote:
> "Randy Brukardt" <randy@rrsoftware.com> writes:
>> For instance:
>>     Num_Outputs : constant Natural :=
>>            (for P of Formal_Params =>
>> Boolean'Pos(P.Is_Operation_Output))'Reduce("+",0);
>>     -- Count "in out" and "out" parameters in a parameter list.
>>
>> Cool, but is this really making the code more readable?
> 
> Is that some kind of syntactic extension in the compiler?  I'm used to
> reduce being an ordinary function.  But "+" in double quotes looks like
> a character string, so the compiler must be figuring out what it does.

That is the operator's name, e.g.

    function "+" (Left, Right : Integer) return Integer;

> It also looks like you can add up booleans, where true=1 and false=0?

Boolean'Pos (X) returns universal integer. Boolean'Pos (False) = 0, 
Boolean'Pos (True) = 1. So the kludge sums all True outcomes of 
Is_Operation_Output.

So it is possible to decipher, but that is by no means Ada (TM).

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de