Re: Ada 2012: In-out parameters for functions

["Yannick Duchêne (Hibou57)" <yannick_duchene@yahoo.fr>]

Le Fri, 03 May 2013 13:42:02 +0200, Yannick Duchêne (Hibou57)  
<yannick_duchene@yahoo.fr> a écrit:
> However, I personally still miss the ability to remind in/in‑out/out  
> modes at the call‑place, and that's the main grief I have with Ada on  
> that topic.

While there is a syntactical tip to get part of this, with the argument  
surrounded in parentheses:


     function Plus_Plus_Ada
       (E : in out Integer)
        return Integer;
     -- Don't laugh, that's not `Ada_Plus_Plus` :D

     function Plus_Plus_Ada
       (E : in out Integer)
       return Integer is
     begin
        E := E + 1;
        return E;
     end;

     -- … Two sample use‑cases

     -- This will pass compilation:

     declare
        I : Integer := 0;
     begin
        I := Plus_Plus_Ada (I);
     end;

     -- This will not pass compilation,
     -- and will give you an error about
     -- `I` which must be a variable:

     declare
        I : Integer := 0;
     begin
        I := Plus_Plus_Ada ((I));
     end;


But that's a bit like the `non null` for access type, which should have  
been the default. Would be better if to have to explicitly says you know  
the argument may be modified, instead of explicitly say you expect it to  
not be modified and add parentheses everywhere.


-- 
“Syntactic sugar causes cancer of the semi-colons.” [1]
“Structured Programming supports the law of the excluded muddle.” [1]
[1]: Epigrams on Programming — Alan J. — P. Yale University