Re: [Boost-users] Boost.Range fancify please

Subject: Re: [Boost-users] Boost.Range fancify please
From: anony (janezz55_at_[hidden])
Date: 2009-12-27 18:52:55

Eric Niebler pravi:
>> Are you certain I am wrong? The array is multidimensional and contiguous
>> in memory. The boost::begin() and boost::end() just return pointers. I
>> have checked if all the floats scale correctly and they do.
> I'm pretty certain. You're straying into undefined behavior by making a
> range using iterators from different arrays.

The make_iterator_range() function sees only 2 pointers and these are
all it cares about. Now, let's check the standard:

ISO-IEC-14882 Section 8.3.4 Array, page 137:

An object of array type contains a contiguously allocated non-
empty set of N sub-objects of type T.

The pointers I provide point to the beginning and the end of the
vertices multidimensional array. The array must be contiguously
allocated, as specified in the standard, hence I don't see which aspect
of what I am doing in undefined, if the functions boost::begin() and
boost::end() work as expected (again, they return pointers, not fancy
iterator objects).

Did I mention the debugger shows everything is just perfect.

>>> Why not just use BOOST_FOREACH correctly?
>>>
>>>    BOOST_FOREACH(float (&rgf)[3], vertices)
>>>      BOOST_FOREACH(float&  f, rgf)
>>>        f *= scale;
>>
>> Double loop, oops. Not fancy enough.
> 
> Are you joking?

I was looking for fancy (i.e. elegant) code, yours is too complicated.