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Date: Tue, 18 Jun 2002 10:49:26 -0400
From: Hyman Rosen <hyrosen@mail.com>
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Subject: Re: Look what I caught! was re:Ada paper critic
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Date: 2002-06-18T10:49:26-04:00
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Darren New wrote:
> You're probably thinking of what I said, which was that a pointer into an
> array is allowed to be increased to point off the end of the array by one
> element, but you can't access it. You don't necessarily get to point two
 > out of bounds, tho.

Right, only one past the end is permitted. As you say, this is used in
algorithms which march a pointer through an array and find it convenient
to post-increment, as in the traditional copying loop of strcpy:

	strcpy(char *to, char *from) { while (*to++ = *from++); }

In C++, this approach has been adopted by the STL algorithms. Whenever
they need to operate on a sequence of elements, that sequence is specified
by a half-open range of iterators, [begin, end), which mirrors the pointer
approach, and in fact pointers are valid iterators, so that STL algorithms
can be used on simple arrays. For example, copy is

	template<typename T> T copy(T begin, T end, T to)
	{ while (begin != end) *to++ = *begin++; return to; }