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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
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 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Ada 2012: In-out parameters for functions
Date: Fri, 03 May 2013 13:54:51 +0200
Organization: Ada @ Home
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Date: 2013-05-03T13:54:51+02:00
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Le Fri, 03 May 2013 13:42:02 +0200, Yannick Duch=C3=AAne (Hibou57)  =

<yannick_duchene@yahoo.fr> a =C3=A9crit:
> However, I personally still miss the ability to remind in/in=E2=80=91o=
ut/out  =

> modes at the call=E2=80=91place, 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 :=3D E + 1;
        return E;
     end;

     -- =E2=80=A6 Two sample use=E2=80=91cases

     -- This will pass compilation:

     declare
        I : Integer :=3D 0;
     begin
        I :=3D 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 :=3D 0;
     begin
        I :=3D 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.


-- =

=E2=80=9CSyntactic sugar causes cancer of the semi-colons.=E2=80=9D [1]
=E2=80=9CStructured Programming supports the law of the excluded muddle.=
=E2=80=9D [1]
[1]: Epigrams on Programming =E2=80=94 Alan J. =E2=80=94 P. Yale Univers=
ity