C++/STL Algorithms Iterator/custom iterater
Содержание
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
*/