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MODULE 31a

THE C++ STL ITERATOR PART 3

What do we have in this page?

1. operator!= prototypes

2. iterator, operator!= program example

3. operator== program example

4. operator< prototype

5. iterator, operator< program example

6. operator<= program example

7. iterator, operator> program example

8. operator>= program example

9. operator+ prototype

10. iterator, operator+ program example

		const reverse_iterator<RandomIterator>& _Right );

		const istream_iterator<Type, CharType, Traits, Distance>& _Left,

		const istream_iterator<Type, CharType, Traits, Distance>& _Right );

		const istreambuf_iterator<CharType, Traits>& _Right );

// iterator, operator!=

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 1; i<=10; ++i) 

        vec.push_back(i);

    vector<int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    // initializing reverse_iterators to the last element

    vector<int>::reverse_iterator rvecpos1 = vec.rbegin(), rvecpos2 = vec.rbegin();

    cout<<"The iterators rvecpos1 and rvecpos2 points to the first\n"

           <<"element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos1 != rvecpos2\n";

    if(rvecpos1 != rvecpos2)

        cout<<"The iterators are not equal."<<endl;

    else

        cout<<"The iterators are equal."<<endl;

    rvecpos1++;

    cout<<"\nThe iterator rvecpos1 now points to the second\n"

           <<"element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos1 != rvecpos2\n";

    if(rvecpos1 != rvecpos2)

        cout<<"The iterators are not equal."<<endl;

    else

        cout<<"The iterators are equal."<<endl;

    return 0;

}

Output:

operator== example

• The return value is true if the iterator objects are equal; false if the iterator objects are not equal.

• One iterator object is equal to another if they address the same elements in a container. If two iterators point to different elements in a container, then they are not equal.

// iterator, operator==

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 11; i<15; ++i)

        vec.push_back(i);

    vector <int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    // initializing reverse_iterators to the last element

    vector<int>::reverse_iterator rvecpos1 = vec.rbegin(), rvecpos2 = vec.rbegin();

    cout<<"\nThe iterators rvecpos1 and rvecpos2 points\nto the first"

            <<"element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos1 == rvecpos2\n";

    if(rvecpos1 == rvecpos2)

        cout<<"The iterators are equal."<<endl;

    else

        cout<<"The iterators are not equal."<<endl;

    rvecpos1++;

    cout<<"\nThe iterator rvecpos1 now points to the second\n"

        <<"element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos1 == rvecpos2\n";

    if(rvecpos1 == rvecpos2)

        cout<<"The iterators are equal."<<endl;

    else

        cout<<"The iterators are not equal."<<endl;

    return 0;

}

Output:

operator< prototype

template<class RandomIterator>

   bool operator<( const reverse_iterator<RandomIterator>& _Left, const reverse_iterator<RandomIterator>& _Right );

Parameters

• The return value is true if the iterator on the left side of the expression is less than the iterator on the right side of the expression; false if it is greater than or equal to the iterator on the right.

• One iterator object is less than another if it addresses an element that occurs earlier in the container than the element addressed by the other iterator object.

• One iterator object is not less than another if it addresses either the same element as the other iterator object or an element that occurs later in the container than the element addressed by the other iterator object.

// iterator, operator<

#include <iterator>

#include <vector>

#include <iostream>

int main()

{

    using namespace std;

    int i;

    vector<int> vec;

    for(i = 10; i<= 17; ++i)

        vec.push_back(i);

    vector<int>::iterator veciter;

    cout<<"The initial vector vec is: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    // initializing reverse_iterators to the last element

    vector<int>::reverse_iterator rvecpos1 = vec.rbegin(), rvecpos2 = vec.rbegin();

    cout<<"The iterators rvecpos1 & rvecpos2 initially point\nto the "

        <<"first element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos1 < rvecpos2\n";

    if(rvecpos1 < rvecpos2)

        cout<<"The iterator rvecpos1 is less than the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is not less than the iterator rvecpos2."<<endl;

    cout<<"\nOperation: rvecpos1 > rvecpos2\n";

    if(rvecpos1 > rvecpos2)

        cout<<"The iterator rvecpos1 is greater than the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is not greater than the iterator rvecpos2."<<endl;

    cout<<"\nOperation: rvecpos2++;\n";

    rvecpos2++;

    cout<<"The iterator rvecpos2 now points to the second\n"

        <<"element in the reversed sequence: "<<*rvecpos2<<endl;

    cout<<"\nOperation: rvecpos1 < rvecpos2\n";

    if(rvecpos1 < rvecpos2)

        cout<<"The iterator rvecpos1 is less than the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is not less than the iterator rvecpos2."<<endl;

    cout<<"\nOperation: rvecpos1 > rvecpos2\n";

    if(rvecpos1 > rvecpos2)

        cout<<"The iterator rvecpos1 is greater than the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is not greater than the iterator rvecpos2."<<endl;

    return 0;

}

Output:

operator<= example

• The return value is true if the iterator on the left side of the expression is less than or equal to the iterator on the right side of the expression; false if it is greater than the iterator on the right.

• One iterator object is less than or equal to another if it addresses the same element or an element that occurs earlier in the container than the element addressed by the other iterator object.

• One iterator object is greater than another if it addresses an element that occurs later in the container than the element addressed by the other iterator object.

// iterator, operator<=

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 10; i<= 15; ++i)

        vec.push_back(i);

    vector <int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    vector <int>::reverse_iterator rvecpos1 = vec.rbegin()+1, rvecpos2 = vec.rbegin();

    cout<<"The iterator rvecpos1 points to the\n"

        <<"second element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"The iterator rvecpos2 points to the\n"

        <<"first element in the reversed sequence: "<<*rvecpos2<<endl;

    cout<<"\nOperation: rvecpos1<=rvecpos2\n";

    if(rvecpos1<=rvecpos2)

        cout<<"The iterator rvecpos1 is less than or\nequal to the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is greater than\nthe iterator rvecpos2."<<endl;

    cout<<"\nOperation: rvecpos2++\n";

    rvecpos2++;

    cout<<"The iterator rvecpos2 now points to the second\n"

        <<"element in the reversed sequence: "<<*rvecpos2<<endl;

    cout<<"\nOperation: rvecpos1 <= rvecpos2\n";

    if(rvecpos1 <= rvecpos2)

        cout<<"The iterator rvecpos1 is less than or\nequal to the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is greater than\nthe iterator rvecpos2."<<endl;

    return 0;

}

Output:

operator> example

• The return value is true if the iterator on the left side of the expression is greater than the iterator on the right side of the expression; false if it is less than or equal to the iterator on the right.

• One iterator object is greater than another if it addresses an element that occurs later in the container than the element addressed by the other iterator object.

• One iterator object is not greater than another if it addresses either the same element as the other iterator object or an element that occurs earlier in the container than the element addressed by the other iterator object.

// iterator, operator>

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 10; i<= 15; ++i)

        vec.push_back(i);

    vector <int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    vector <int>::reverse_iterator rvecpos1 = vec.rbegin(), rvecpos2 = vec.rbegin();

    cout<<"The iterators rvecpos1 & rvecpos2 point to the\n"

        <<"second element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos2 > rvecpos1\n";

    if(rvecpos2 > rvecpos1)

            cout<<"The iterator rvecpos2 is greater than\nthe iterator rvecpos1."<<endl;

    else

            cout<<"The iterator rvecpos2 is not greater than\nthe iterator rvecpos1."<<endl;

    cout<<"\nOperation: rvecpos2++\n";

    rvecpos2++;

    cout<<"The iterator rvecpos2 now points to the second\n"

            <<"element in the reversed sequence: "<<*rvecpos2<<endl;

    cout<<"\nOperation: rvecpos2 > rvecpos1\n";

    if(rvecpos2 > rvecpos1)

            cout<<"The iterator rvecpos2 is greater than\nthe iterator rvecpos1."<<endl;

    else

            cout<<"The iterator rvecpos2 is not greater than\nthe iterator rvecpos1."<<endl;

    return 0;

}

Output:

operator>= example

• The return value is true if the iterator on the left side of the expression is greater than or equal to the iterator on the right side of the expression; false if it is less than the iterator on the right.

• One iterator object is greater than or equal to another if it addresses the same element or an element that occurs later in the container than the element addressed by the other iterator object.

• One iterator object is less than another if it addresses an element that occurs earlier in the container than the element addressed by the other iterator object.

// iterator, operator>=

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 10; i<= 15; ++i)

        vec.push_back(i);

    vector <int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    vector <int>::reverse_iterator rvecpos1 = vec.rbegin(), rvecpos2 = vec.rbegin();

    cout<<"The iterators rvecpos1 & rvecpos2 point to the\n"

            <<"second element in the reversed sequence: "<<*rvecpos1<<endl;

    cout<<"\nOperation: rvecpos2 >= rvecpos1\n";

    if(rvecpos2 >= rvecpos1)

        cout<<"The iterator rvecpos2 is greater than or\nequal to the iterator rvecpos1."<<endl;

    else

        cout<<"The iterator rvecpos2 is not greater than\nthe iterator rvecpos1."<<endl;

    cout<<"\nOperation: rvecpos2++\n";

    rvecpos2++;

    cout<<"The iterator rvecpos2 now points to the second\nelement in the reversed sequence: "<<*rvecpos2<<endl;

    cout<<"\nOperation: rvecpos2 >= rvecpos1\n";

    if(rvecpos2 >= rvecpos1)

        cout<<"The iterator rvecpos2 is greater than\nor equal to the iterator rvecpos1."<<endl;

    else

        cout<<"The iterator rvecpos2 is not greater than\nthe iterator rvecpos1."<<endl;

    cout<<"\nOperation: rvecpos1 >= rvecpos2\n";

    if(rvecpos1 >= rvecpos2)

        cout<<"The iterator rvecpos1 is greater than\nor equal to the iterator rvecpos2."<<endl;

    else

        cout<<"The iterator rvecpos1 is not greater than\nthe iterator rvecpos2."<<endl;

    return 0;

}

Output:

operator+ prototype

template<class RandomIterator>

   reverse_iterator<RandomIterator> operator+( typename reverse_iterator<Iterator>::difference_type _Off,

      const reverse_iterator<RandomIterator>& _Right );

Parameters

• The return value is the sum _Right + _Off.

// iterator, operator+

#include <iterator>

#include <vector>

#include <iostream>

using namespace std;

int main()

{

    int i;

    vector<int> vec;

    for(i = 10; i<=15; ++i)

        vec.push_back(i);

    vector<int>::iterator veciter;

    cout<<"The vector vec data: ";

    for(veciter = vec.begin(); veciter != vec.end(); veciter++)

        cout<<*veciter<<" ";

    cout<<endl;

    vector<int>::reverse_iterator rveciter1 = vec.rbegin();

    cout<<"\nThe iterator rveciter1 initially points to\n"

            <<"the first element in the reversed sequence: "<<*rveciter1<<endl;

    cout<<"\nOperation: rveciter1 = diff + rveciter1\n";

    vector<int>::difference_type diff = 4;

    rveciter1 = diff + rveciter1;

    cout<<"The iterator rveciter1 now points to the fifth\n"

            <<"element in the reversed sequence: "<<*rveciter1<<endl;

   return 0;

}

Output:

tenouk C++ STL tutorial

Further C++ STL iterators related reading:

1. The source code in text for this tutorial is available inC++ STL Iterator source code.

2. C++ Templates programming tutorials.

3. Acomplete C Standard Library.

4. Acomplete C++ Standard Library documentation that includes STL.

5. Check thebest selling C / C++ and STL books at Amazon.com.

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