C++ Tutorial/STL Algorithms Iterator/custom iterater

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Create back_insert_iterator

<source lang="cpp">/* 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.
*/
  1. include <iostream>
  2. include <vector>
  3. 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);

}</source>

1 2 3
1 2 3 44 55
1 2 3 44 55 1 2 3 44 55

front_insert_iterator

<source lang="cpp">/* 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.
*/
  1. include <iostream>
  2. include <list>
  3. 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);

}</source>

3 2 1
55 44 3 2 1
1 2 3 44 55 55 44 3 2 1

insert_iterator

<source lang="cpp">/* 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.
*/
  1. include <iostream>
  2. include <set>
  3. include <list>
  4. 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: ");

}</source>

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

<source lang="cpp">/* 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.
*/
  1. include <iostream>
  2. include <set>
  3. 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;

}

  1. 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);

}</source>

1 2 3
1 2 3 44 55
-4 1 2 3 5 13 33 44 55 67