C++ Tutorial/STL Algorithms Iterator/custom iterater
Содержание
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. */
- 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);
}</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. */
- 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);
}</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. */
- 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: ");
}</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. */
- 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);
}</source>
1 2 3 1 2 3 44 55 -4 1 2 3 5 13 33 44 55 67