Re: Ada 2012 Constraints (WRT an Ada IR)

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2016-12-14 17:31, G.B. wrote:
> On 14/12/2016 13:52, Dmitry A. Kazakov wrote:
>> On 14/12/2016 13:44, G.B. wrote:
>>> On 14/12/2016 12:25, Dmitry A. Kazakov wrote:
>>>
>>>> That is the problem with implied contracts. Is this legal:
>>>>
>>>> begin
>>>>    loop
>>>>       X (Read (Stream));
>>>>    end loop;
>>>> exception
>>>>    when Constraint_Error =>
>>>>       null;
>>>> end;
>>>
>>>    "Assertions are not an input checking mechanism"
>>>    "To avoid a common misunderstanding, make sure to note
>>> that each of the contracts discussed holds between a routine
>>> (the supplier) and another routine (its caller): we are concerned
>>> about software-to-software communication, not software-to-human
>>> or software-to-outside-world. (...) Here there is no substitute
>>> for the usual condition-checking constructs, include the venerable
>>> IF ... THEN ...; the exception handling mechanism ... may also be
>>> helpful ". [1]
>>>
>>> [1] Meyer, Bertrand: OOSC2, 2nd ed, §11.6
>>
>> Is it legal or not?
>
> Like you have said, "It is about formal language-supported contracts
> and all sorts of other contracts". So, I think there is enough material
> there to conclude that this kind or that kind of contract should
> be legally dominating a particular program design decision.

That is no answer. A program is either legal or not. The program is 
legal. The contract you implied is violated. Thus what you called 
contract is not a formal contract. q.e.d.

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