Apache C++ Standard Library Reference Guide

## includes()

Library: Algorithms

    Function

- Local Index
- Summary
- Synopsis
- Description
- Complexity
- Example
- See Also
- Standards Conformance

### Local Index

No Entries

### Summary

An algorithm that returns true if every element in one sorted sequence is contained in another sorted sequence

### Synopsis

    #include <algorithm>

    namespace std {
      template <class InputIterator1, class InputIterator2>
      bool includes(InputIterator1 start1, InputIterator1 finish1,
                    InputIterator2 start2,
                    InputIterator2 finish2);

      template <class InputIterator1, class InputIterator2,
               class Compare>
      bool includes(InputIterator1 start1, InputIterator1 finish1,
                    InputIterator2 start2,
                    InputIterator2 finish2, Compare comp);
    }

### Description

The `includes()` algorithm compares two sorted sequences and returns `true` if every element in the range `[start2, finish2)` is contained in the range `[start1, finish1)`. It returns `false` otherwise. `includes()` assumes that the sequences are sorted using `operator<()`, or using the predicate `comp`.

### Complexity

At most `((finish1 - start1) + (finish2 - start2)) * 2 - 1` comparisons are performed.

### Example

    //
    //  includes.cpp
    //

    #include <algorithm>   // for includes
    #include <iostream>    // for cout, endl
    #include <set>         // for set

    int main ()
    {
        // Typedefs for convenience.
        typedef std::set<int, std::less<int>, std::allocator<int> >
                Set;
        typedef std::ostream_iterator<int, char,
                                      std::char_traits<char> >
                 os_iter;

        int a1[] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
        int a2[] = { 2, 4, 6, 8, 10, 12 };
        int a3[] = { 3, 5, 7, 8 };

        // Initialize three sets.
        Set all   (a1, a1 + sizeof a1 / sizeof *a1);
        Set even  (a2, a2 + sizeof a2 / sizeof *a2);
        Set other (a3, a3 + sizeof a3 / sizeof *a3);

        // Demonstrate includes.
        std::cout << "The set: ";
        std::copy (all.begin (), all.end (),
                   os_iter (std::cout, " "));

        bool answer = std::includes (all.begin (), all.end (),
                                     other.begin (), other.end ());

        std::cout << std::endl
                  << (answer ? "INCLUDES " : "DOES NOT INCLUDE ");
        std::copy (other.begin (), other.end (),
                   os_iter (std::cout, " "));

        answer = std::includes (all.begin (), all.end (),
                                even.begin (), even.end ());

        std::cout << ", and" << std::endl
                  << (answer ? "INCLUDES" : "DOES NOT INCLUDE ");

        std::copy (even.begin (), even.end (),
                   os_iter (std::cout, " "));

        std::cout << std::endl << std::endl;

        return 0;
    }

    Program Output:
    The set: 1 2 3 4 5 6 7 8 9 10
    INCLUDES 3 5 7 8 , and
    DOES NOT INCLUDE 2 4 6 8 10 12

### See Also

`set_union()`, `set_intersection()`, `set_difference()`, `set_symmetric_difference()`

### Standards Conformance

ISO/IEC 14882:1998 -- International Standard for Information Systems -- Programming Language C++, Section 25.3.5.1