function template
<algorithm>

# std::is_sorted

default (1) ```template bool is_sorted (ForwardIterator first, ForwardIterator last); ``` ```template bool is_sorted (ForwardIterator first, ForwardIterator last, Compare comp);```
Check whether range is sorted
Returns `true` if the range `[first,last)` is sorted into ascending order.

The elements are compared using `operator<` for the first version, and comp for the second.

The behavior of this function template is equivalent to:
 ``123456789101112`` ``````template bool is_sorted (ForwardIterator first, ForwardIterator last) { if (first==last) return true; ForwardIterator next = first; while (++next!=last) { if (*next<*first) // or, if (comp(*next,*first)) for version (2) return false; ++first; } return true; }``````

### Parameters

first, last
Forward iterators to the initial and final positions of the sequence. The range checked 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.
comp
Binary function that accepts two elements in the range as arguments, and returns a value convertible to `bool`. The value returned indicates whether the element passed as first argument is considered to go before the second in the specific strict weak ordering it defines.
The function shall not modify any of its arguments.
This can either be a function pointer or a function object.

### Return value

`true` if the range `[first,last)` is sorted into ascending order, `false` otherwise.

If the range `[first,last)` contains less than two elements, the function always returns `true`.

### Example

 ``1234567891011121314151617181920212223`` ``````// is_sorted example #include // std::cout #include // std::is_sorted, std::prev_permutation #include // std::array int main () { std::array foo {2,4,1,3}; do { // try a new permutation: std::prev_permutation(foo.begin(),foo.end()); // print range: std::cout << "foo:"; for (int& x:foo) std::cout << ' ' << x; std::cout << '\n'; } while (!std::is_sorted(foo.begin(),foo.end())); std::cout << "the range is sorted!\n"; return 0; }``````

Output:
 ```foo: 2 3 4 1 foo: 2 3 1 4 foo: 2 1 4 3 foo: 2 1 3 4 foo: 1 4 3 2 foo: 1 4 2 3 foo: 1 3 4 2 foo: 1 3 2 4 foo: 1 2 4 3 foo: 1 2 3 4 the range is sorted! ```

### Complexity

Up to linear in one less than the distance between first and last: Compares pairs of elements until a mismatch is found.

### Data races

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

### Exceptions

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