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Date: Mon, 07 Jun 2010 17:50:25 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Newsgroups: comp.lang.ada
Subject: Re: Ada noob here! Is Ada widely used?
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Date: 2010-06-07T17:50:26+02:00
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On 07.06.10 17:09, Dmitry A. Kazakov wrote:
> On Mon, 07 Jun 2010 17:00:07 +0200, Georg Bauhaus wrote:
> 
>> On 07.06.10 16:51, Dmitry A. Kazakov wrote:
>>> On Mon, 07 Jun 2010 16:12:38 +0200, Georg Bauhaus wrote:
>>>
>>>> On 07.06.10 14:22, Dmitry A. Kazakov wrote:
>>>
>>>>> This includes the exceptional ones. When bug
>>>>> happens, the program is in no state.
>>>>
>>>> Erh, are you sure?
>>>
>>> Yes I am. Any program state is defined, it has some sematic interpretation
>>> in the domain. Bug is when you have lost this synchronization. Meaningless
>>> state is no state.
>>
>> Then what constitutes a bug?
>>
>>   procedure add_to_account(Number: in out  Account_ID; sum: Money) is
>>      client_account: Account := Find_Account(Number);
>>   begin
>>     -- FIXME: not ready, using dummy account
>>     client_account := Make_new_Account;
>>   end add_to_account;
> 
> Where is a problem?

The above program, if it enters production, has
a bug, IMHO:

  if Passed_In > 0.0 then
    Lock.Seize;
    was := amount_in_account(123);
    add_to_account(123, sum => Passed_In);
    is := amount_in_account(123);
    Lock.Release;

    -- assume add_to_account is correct
    send(other_bank, is - was);

Program state is meaningful, if buggy.

Or are you defining a bug to be a state of the program
to which you are unable to assign meaning?