Mega Code Archive
Template class for insert iterator for associative containers
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/* 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
*/
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