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Date: Wed, 09 Mar 2005 12:17:37 +0100
From: Georg Bauhaus <bauhaus@futureapps.de>
Organization: future apps GmbH
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Newsgroups: comp.lang.ada,comp.lang.c++,comp.realtime,comp.software-eng
Subject: Re: Teaching new tricks to an old dog (C++ -->Ada)
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Date: 2005-03-09T12:15:56+01:00
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Ioannis Vranos wrote:
> Pascal Obry wrote:

>>> The C++ equivalent:

>>> for(vector<int>::size_type i=0; i<Data.size(); ++i)
>>> {
>>>     if (Data[i]== 1)

>>    for K in Data'Range loop
>>       ... Data(k)...
>> 
> ISO C++ speaking, one may use vector::at() which provides boundary 
> checking, however the aforementioned way is *always* 100% safe

The loop happens to be "safe" but not by the scope and range
of i. The loops aren't equivalent, strictly speaking, because
the loop counter doesn't act as a constant.
Disciplined use of iterators/pointers/indices is not the same
thing as a constant loop index:

  for (vector<int>::size_type i=0; i<Data.size(); ++i) {
    if (Data.at(i)== 1) 
      i = 100;
  }

This text is compiled without complaint as should be, because it _might_
have been the programmer's intention to set the index to some value off
bounds, and he/she _might_ not have wanted a while loop instead of a for
loop.

Some languages provide language facilities to express this difference.
A constant loop index can make some proofs easier.

Georg