function template
<algorithm>

# std::reverse

```template <class BidirectionalIterator>
void reverse (BidirectionalIterator first, BidirectionalIterator last);```
Reverse range
Reverses the order of the elements in the range `[first,last)`.

The function calls iter_swap to swap the elements to their new locations.

The behavior of this function template is equivalent to:
 ``12345678`` ``````template void reverse (BidirectionalIterator first, BidirectionalIterator last) { while ((first!=last)&&(first!=--last)) { std::iter_swap (first,last); ++first; } }``````

### Parameters

first, last
Bidirectional iterators to the initial and final positions of the sequence to be reversed. The range used is `[first,last)`, which contains all the elements between first and last, including the element pointed by first but not the element pointed by last.
BidirectionalIterator shall point to a type for which swap is properly defined.

none

### Example

 ``123456789101112131415161718192021`` ``````// reverse algorithm example #include // std::cout #include // std::reverse #include // std::vector int main () { std::vector myvector; // set some values: for (int i=1; i<10; ++i) myvector.push_back(i); // 1 2 3 4 5 6 7 8 9 std::reverse(myvector.begin(),myvector.end()); // 9 8 7 6 5 4 3 2 1 // print out content: std::cout << "myvector contains:"; for (std::vector::iterator it=myvector.begin(); it!=myvector.end(); ++it) std::cout << ' ' << *it; std::cout << '\n'; return 0; }``````

Output:
 ```myvector contains: 9 8 7 6 5 4 3 2 1 ```

### Complexity

Linear in half the distance between first and last: Swaps elements.

### Data races

The objects in the range `[first,last)` are modified.

### Exceptions

Throws if either an element swap or an operation on an iterator throws.
Note that invalid arguments cause undefined behavior.