Cpp > Programs

cpp unary_function example and tutorials

#include <iostream>
#include <vector>
#include <iterator>
#include <functional>
#include <algorithm>
using namespace std;

const int VectorSize = 5;

template<class T>
class Print: public unary_function<T, void>
{
public:
void operator()(T& arg1)
{
cout << arg1 << " ";
}
};

template<class T>
class GreaterThanTwo: public unary_function<T, bool>
{
public:
bool operator()(T& arg1)
{
return (arg1 > 2);
}
};

template<class Container, class Iterator>
void ShowElement(Container& c, Iterator& itor);

int main()
{
Print<int> DoPrint;
vector<int> vInt(VectorSize);
typedef vector<int>::iterator Itor;

for (int i = 0; i < VectorSize; ++i)
vInt[i] = i;

Itor first = vInt.begin();
Itor last = vInt.end();

cout << "for_each()\n";
for_each(first, last, DoPrint);
cout << "\n";

Itor retItor = find(first, last, 2);
cout << "find(first, last, 2) = ";
ShowElement(vInt, retItor);
cout << "\n";

retItor = find(first, last, 10);
cout << "find(first, last, 10) = ";
ShowElement(vInt, retItor);
cout << "\n";

GreaterThanTwo<int> IsGreaterThanTwo;
retItor = find_if(first, last, IsGreaterThanTwo);
cout << "find(first, last, IsGreaterThanTwo) = ";
ShowElement(vInt, retItor);
cout << "\n";

int retSize = count(first, last, 3);
cout << "count(first, last, 3) = " << retSize << "\n";

retSize = count_if(first, last, IsGreaterThanTwo);
cout << "count_if(first, last, IsGreaterThanTwo) = " << retSize << "\n";

return 0;
}

template<class Container, class Iterator>
void ShowElement(Container& c, Iterator& itor)
{
if (itor != c.end())
cout << *itor;
else
cout << "last";
}