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From: Pete Becker<pete@versatilecoding.com>
Newsgroups: comp.std.c++
Subject: Re: [alg.equal]: really requires a bidirectional iterator
Date: Sat,  3 Sep 2011 14:36:27 -0700 (PDT)
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Xref: x330-a1.tempe.blueboxinc.net comp.std.c++:270

On 2011-09-02 17:45:58 +0000, Krzysztof Żelechowski said:

>  The expression (*i == *(first2 + (i - first1))) does not have a meaning for
>  input iterators.

See [alg.general]/12:

	In the description of the algorithms operators + and - are used for some
	of the iterator categories for which they do not have to be defined. In these
	cases the semantics of a+n is the same as that of

		X tmp = a;
  		advance(tmp, n);
  		return tmp;

	and that of b-a is the same as of

		return distance(a, b);

-- 
  Pete
Roundhouse Consulting, Ltd. (www.versatilecoding.com) Author of "The
Standard C++ Library Extensions: a Tutorial and Reference
(www.petebecker.com/tr1book)


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