Книга: Standard Template Library Programmer



Category: algorithms

Component type: function


template <class ForwardIterator, class OutputIterator>
OutputIterator rotate_copy(ForwardIterator first, ForwardIterator middle, ForwardIterator last, OutputIterator result);


Rotate_copy copies elements from the range [first, last) to the range [result, result + (last – first)) such that *middle is copied to *result, *(middle + 1) is copied to *(result + 1), and so on. Formally, for every integer n such that 0 <= n < last – first, rotate_copy performs the assignment *(result + (n + (last – middle)) % (last – first)) = *(first + n). Rotate_copy is similar to copy followed by rotate, but is more efficient. The return value is result + (last – first).


Defined in the standard header algorithm, and in the nonstandard backward-compatibility header algo.h.

Requirements on types

• ForwardIterator is a model of Forward Iterator.

• OutputIterator is a model of Output Iterator.

• ForwardIterator's value type is convertible to a type in OutputIterator's set of value types.


• [first, middle) is a valid range.

• [middle, last) is a valid range. [1]

• There is enough space to hold all of the elements being copied. More formally, the requirement is that [result, result + (last – first)) is a valid range.

• The ranges [first, last) and [result, result + (last – first)) do not overlap.


Linear. Rotate_copy performs exactly last – first assignments.


const char alpha[] = "abcdefghijklmnopqrstuvwxyz";
rotate_copy(alpha, alpha + 13, alpha + 26, ostream_iterator<char>(cout));
// The output is nopqrstuvwxyzabcdefghijklm


[1] It follows from these two requirements that [first, last) is a valid range.

See also

rotate, copy.

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