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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
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Date: Tue, 31 Jan 2012 00:11:43 +0100
Organization: Ada @ Home
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Date: 2012-01-31T00:11:43+01:00
List-Id: <comp.lang.ada>


Hi people out there,

A matter of style or more than style.

I wanted to add a post=E2=80=91condition to a function to make its speci=
fication  =

more predictive. The function returns a type =C3=A0 la SML, i.e. instead=
 of a  =

boolean status on failure along with an undefined value, it returns a  =

record containing nothing. There is an obvious case where it is sure to =
 =

fail, so I wanted to express this obvious behavior in a post=E2=80=91con=
dition.  =

But I can't make up my mind, can't clearly feel if that's simply silly a=
nd  =

useless wast of source or else.

May I request for your opinion on the simple sample please ? The main  =

point is on the function post=E2=80=91condition at the end.


    type Parsed_Type (Status : Parsed_Status_Type) is record
       case Status is
          when Parsed =3D>
             Instance : Instance_Type;
          when Format_Error =3D>
             null;
       end case;
    end record; -- Parsed_Type

    function Parsed (S : String) return Parsed_Type
       with Post =3D>
         (if S'Length not in Image_Length_Type then
             Parsed'Result.Status =3D Format_Error);
          -- There may be other failure conditions.


Is such a post=E2=80=91condition a good or bad practice in your humble o=
r  =

authoritative opinion ?

Keep in mind there may be many other cases where =E2=80=9CParsed'Result.=
Status =3D  =

Format_Error=E2=80=9D could be True; the one in the Post is not the only=
 possible  =

one.


-- =

=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