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From: =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?=
 =?utf-8?Q?=29?=
 <yannick_duchene@yahoo.fr>
Newsgroups: comp.lang.ada
Subject: Re: Seeking for papers about tagged types vs access to subprograms
Date: Fri, 10 May 2013 06:16:46 +0200
Organization: Ada @ Home
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Date: 2013-05-10T06:16:46+02:00
List-Id: <comp.lang.ada>

Le Fri, 10 May 2013 05:29:53 +0200, Yannick Duch=C3=AAne (Hibou57)  =

<yannick_duchene@yahoo.fr> a =C3=A9crit:
> [=E2=80=A6] A simple example, is paired invocation, where whenever a s=
ub=E2=80=91program  =

> is is invoked, sooner or later, another sub=E2=80=91program must be in=
voked too  =

> on the same argument, ex. like `Open` and later `Close`. This cannot b=
e  =

> expressed with types and indeed requires assertions.
>
> But saying =E2=80=9Cweak=E2=80=9D may be erroneously interpreted, and =
then, the type is  =

> still the first place to holds the validity rules. In the example abov=
e,  =

> the paired invocation requirement, could be expressed in the type owni=
ng  =

> these two primitives [=E2=80=A6]

No, what I said on this is wrong, due to lack of precision. This have to=
  =

be an assertion on the outer level, the state of the enclosing scope of =
 =

the operations (an implicit value which cannot be explicitly referred to=
  =

as a whole with Ada).

-- =

=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