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Standard Template Library Programmer's Guide
(document number: 007-3426-004 / published: 1999-05-21) table of contents | additional info | download
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is_sorted


Category: algorithms	Component type: function

Prototype

Is_sorted is an overloaded name; there are actually two is_sorted functions.

template <class ForwardIterator>
bool is_sorted(ForwardIterator first, ForwardIterator last)

template <class ForwardIterator, class StrictWeakOrdering>
bool is_sorted(ForwardIterator first, ForwardIterator last,
               StrictWeakOrdering comp)

Description

Is_sorted returns true if the range [first, last) is sorted in ascending order, and false otherwise.

The two versions of is_sorted differ in how they define whether one element is less than another. The first version compares objects using operator<, and the second compares objects using the function object comp. The first version of is_sorted returns true if and only if, for every iterator i in the range [first, last - 1), *(i + 1) < *i is false. The second version returns true if and only if, for every iterator i in the range [first, last - 1), comp(*(i + 1), *i) is false

Definition

Defined in algo.h.

Requirements on types

For the first version:

ForwardIterator is a model of Forward Iterator.
ForwardIterator's value type is a model of LessThan Comparable.
The ordering on objects of ForwardIterator's value type is a strict weak ordering, as defined in the LessThan Comparable requirements.

For the second version:

ForwardIterator is a model of Forward Iterator.
StrictWeakOrdering is a model of Strict Weak Ordering.
ForwardIterator's value type is convertible to StrictWeakOrdering's argument type.

Preconditions

[first, last) is a valid range.

Complexity

Linear. Zero comparisons if [first, last) is an empty range, otherwise at most (last - first) - 1 comparisons.

Example

int A[] = {1, 4, 2, 8, 5, 7};
const int N = sizeof(A) / sizeof(int);

assert(!is_sorted(A, A + N));
sort(A, A + N);
assert(is_sorted(A, A + N));