std::istream_iterator

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

// istream_iterator example
#include <iostream> // std::cin, std::cout
#include <iterator> // std::istream_iterator
int main () {
 double value1, value2;
 std::cout << "Please, insert two values: ";
 std::istream_iterator<double> eos; // end-of-stream iterator
 std::istream_iterator<double> iit (std::cin); // stdin iterator
 if (iit!=eos) value1=*iit;
 ++iit;
 if (iit!=eos) value2=*iit;
 std::cout << value1 << "*" << value2 << "=" << (value1*value2) << '\n';
 return 0;
}

Please, insert two values: 2 32
2*32=64

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29

template <class T, class charT=char, class traits=char_traits<charT>, class Distance=ptrdiff_t>
 class istream_iterator :
 public iterator<input_iterator_tag, T, Distance, const T*, const T&>
{
 basic_istream<charT,traits>* in_stream;
 T value;
public:
 typedef charT char_type;
 typedef traits traits_type;
 typedef basic_istream<charT,traits> istream_type;
 istream_iterator() : in_stream(0) {}
 istream_iterator(istream_type& s) : in_stream(&s) { ++*this; }
 istream_iterator(const istream_iterator<T,charT,traits,Distance>& x)
 : in_stream(x.in_stream), value(x.value) {}
 ~istream_iterator() {}
 const T& operator*() const { return value; }
 const T* operator->() const { return &value; }
 istream_iterator<T,charT,traits,Distance>& operator++() {
 if (in_stream && !(*in_stream >> value)) in_stream=0;
 return *this;
 }
 istream_iterator<T,charT,traits,Distance> operator++(int) {
 istream_iterator<T,charT,traits,Distance> tmp = *this;
 ++*this;
 return tmp;
 }
};