Boost.Range documentation update iteration.

[SVN r61647]

doc/reference/algorithm_ext/copy_n.qbk

@@ -0,0 +1,32 @@
+[section:copy_n copy_n]
+
+[heading Prototype]
+
+``
+template<class SinglePassRange, class Size, class OutputIterator>
+OutputIterator copy_n(const SinglePassRange& rng, Size n, OutputIterator out);
+``
+
+[heading Description]
+
+`copy_n` is provided to completely replicate the standard algorithm header,
+it is preferable to use Range Adaptors and the extension functions to achieve
+the same result with greater safety.
+
+`copy_n` copies elements from `[boost::begin(rng), boost::begin(rng) + n)` to the range `[out, out + n)`
+
+[heading Definition]
+
+Defined in the header file `boost/range/algorithm_ext/copy_n.hpp`
+
+[heading Requirements]
+
+# `SinglePassRange` is a model of the __single_pass_range__ Concept.
+# `Size` is a model of the `Integer` Concept.
+# `OutputIterator` is a model of the `OutputIteratorConcept`.
+
+[heading Complexity]
+
+Linear. Exactly `n` elements are copied.
+
+[endsect]