C++ Tutorial/STL Algorithms Iterator/custom iterater

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Create back_insert_iterator

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <vector>
#include <algorithm>
/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;
    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << " ";
    }
    std::cout << std::endl;
}
using namespace std;
int main()
{
    vector<int> coll;
    // create back inserter for coll
    // - inconvenient way
    back_insert_iterator<vector<int> > iter(coll);
    // insert elements with the usual iterator interface
    *iter = 1;
    iter++;
    *iter = 2;
    iter++;
    *iter = 3;
    PRINT_ELEMENTS(coll);
    // create back inserter and insert elements
    // - convenient way
    back_inserter(coll) = 44;
    back_inserter(coll) = 55;
    PRINT_ELEMENTS(coll);
    // use back inserter to append all elements again
    // - reserve enough memory to avoid reallocation
    coll.reserve(2*coll.size());
    copy (coll.begin(), coll.end(),    // source
          back_inserter(coll));        // destination
    PRINT_ELEMENTS(coll);
}
1 2 3
1 2 3 44 55
1 2 3 44 55 1 2 3 44 55

front_insert_iterator

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <list>
#include <algorithm>
using namespace std;
/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;
    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << " ";
    }
    std::cout << std::endl;
}
int main()
{
    list<int> coll;
    // create front inserter for coll
    // - inconvenient way
    front_insert_iterator<list<int> > iter(coll);
    // insert elements with the usual iterator interface
    *iter = 1;
    iter++;
    *iter = 2;
    iter++;
    *iter = 3;
    PRINT_ELEMENTS(coll);
    // create front inserter and insert elements
    // - convenient way
    front_inserter(coll) = 44;
    front_inserter(coll) = 55;
    PRINT_ELEMENTS(coll);
    // use front inserter to insert all elements again
    copy (coll.begin(), coll.end(),    // source
          front_inserter(coll));       // destination
    PRINT_ELEMENTS(coll);
}
3 2 1
55 44 3 2 1
1 2 3 44 55 55 44 3 2 1

insert_iterator

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <set>
#include <list>
#include <algorithm>
using namespace std;
/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;
    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << " ";
    }
    std::cout << std::endl;
}
int main()
{
    set<int> coll;
    // create insert iterator for coll
    // - inconvenient way
    insert_iterator<set<int> > iter(coll,coll.begin());
    // insert elements with the usual iterator interface
    *iter = 1;
    iter++;
    *iter = 2;
    iter++;
    *iter = 3;
    PRINT_ELEMENTS(coll,"set:  ");
    // create inserter and insert elements
    // - convenient way
    inserter(coll,coll.end()) = 44;
    inserter(coll,coll.end()) = 55;
    PRINT_ELEMENTS(coll,"set:  ");
    // use inserter to insert all elements into a list
    list<int> coll2;
    copy (coll.begin(), coll.end(),           // source
          inserter(coll2,coll2.begin()));     // destination
    PRINT_ELEMENTS(coll2,"list: ");
    // use inserter to reinsert all elements into the list before the second el
ement
    copy (coll.begin(), coll.end(),           // source
          inserter(coll2,++coll2.begin()));   // destination
    PRINT_ELEMENTS(coll2,"list: ");
}
set:  1 2 3
set:  1 2 3 44 55
list: 1 2 3 44 55
list: 1 1 2 3 44 55 2 3 44 55

template class for insert iterator for associative containers

/* The following code example is taken from the book
 * "The C++ Standard Library - A Tutorial and Reference"
 * by Nicolai M. Josuttis, Addison-Wesley, 1999
 *
 * (C) Copyright Nicolai M. Josuttis 1999.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#include <iostream>
#include <set>
#include <algorithm>
using namespace std;

/* PRINT_ELEMENTS()
 * - prints optional C-string optcstr followed by
 * - all elements of the collection coll
 * - separated by spaces
 */
template <class T>
inline void PRINT_ELEMENTS (const T& coll, const char* optcstr="")
{
    typename T::const_iterator pos;
    std::cout << optcstr;
    for (pos=coll.begin(); pos!=coll.end(); ++pos) {
        std::cout << *pos << " ";
    }
    std::cout << std::endl;
}

#include <iterator>
/* template class for insert iterator for associative containers
 */
template <class Container>
class asso_insert_iterator
 : public std::iterator <std::output_iterator_tag,
                         void, void, void, void>
{
  protected:
    Container& container;    // container in which elements are inserted
  public:
    // constructor
    explicit asso_insert_iterator (Container& c) : container(c) {
    }
    // assignment operator
    // - inserts a value into the container
    asso_insert_iterator<Container>&
    operator= (const typename Container::value_type& value) {
        container.insert(value);
        return *this;
    }
    // dereferencing is a no-op that returns the iterator itself
    asso_insert_iterator<Container>& operator* () {
        return *this;
    }
    // increment operation is a no-op that returns the iterator itself
    asso_insert_iterator<Container>& operator++ () {
        return *this;
    }
    asso_insert_iterator<Container>& operator++ (int) {
        return *this;
    }
};
/* convenience function to create the inserter
 */
template <class Container>
inline asso_insert_iterator<Container> asso_inserter (Container& c)
{
    return asso_insert_iterator<Container>(c);
}

int main()
{
    set<int> coll;
    // create inserter for coll
    // - inconvenient way
    asso_insert_iterator<set<int> > iter(coll);
    // insert elements with the usual iterator interface
    *iter = 1;
    iter++;
    *iter = 2;
    iter++;
    *iter = 3;
    PRINT_ELEMENTS(coll);
    // create inserter for coll and insert elements
    // - convenient way
    asso_inserter(coll) = 44;
    asso_inserter(coll) = 55;
    PRINT_ELEMENTS(coll);
    // use inserter with an algorithm
    int vals[] = { 33, 67, -4, 13, 5, 2 };
    copy (vals, vals+(sizeof(vals)/sizeof(vals[0])),  // source
          asso_inserter(coll));                       // destination
    PRINT_ELEMENTS(coll);
}
1 2 3
1 2 3 44 55
-4 1 2 3 5 13 33 44 55 67