Iterators
Stream iterator that provides iterator capabilities for istreams. This iterator allows generic algorithms to be used directly on streams.
#include <iterator>
template <class T, class Distance = ptrdiff_t> class istream_iterator : public input_iterator;
Stream iterators provide the standard iterator interface for input and output streams.
The class istream_iterator reads elements from an input stream (using operator >>). A value of type T is retrieved and stored when the iterator is constructed and each time operator++ is called. The iterator will be equal to the end-of-stream iterator value if the end-of-file is reached. Use the constructor with no arguments to create an end-of-stream iterator. The only valid use of this iterator is to compare to other iterators when checking for end of file. Do not attempt to dereference the end-of-stream iterator; it plays the same role as the past-the-end iterator provided by the end() function of containers. Since an istream_iterator is an input iterator, you cannot assign to the value returned by dereferencing the iterator. This also means that istream_iterators can only be used for single pass algorithms.
Since a new value is read every time the operator++ is used on an istream_iterator, that operation is not equality-preserving. This means that i == j does not mean that ++i == ++j (although two end-of-stream iterators are always equal).
template <class T, class Distance = ptrdiff_t>
class istream_iterator : public input_iterator<T, Distance>
{
public:
istream_iterator();
istream_iterator (istream&);
istream_iterator (const istream_iterator <T, Distance>&);
~istream_itertor ();
const T& operator*() const;
const T* operator ->() const;
istream_iterator <T, Distance>& operator++();
istream_iterator <T, Distance> operator++ (int)
};
// Non-member Operators
template <class T, class Distance>
bool operator== (const istream_iterator<T, Distance>&,
const istream_iterator<T, Distance>&);
istream_iterator ();
Construct an end-of-stream iterator. This iterator can be used to compare against an end-of-stream condition. Use it to provide end iterators to algorithms
istream_iterator (istream& s);
Construct an istream_iterator on the given stream.
istream_iterator (const istream_iterator<T, Distance>& x);
Copy constructor.
~istream_iterator ();
Destructor.
const T& operator* () const;
Return the current value stored by the iterator.
const T* operator-> () const;
Return a poinster to the current value stored by the iterator.
istream_iterator<T, Distance>& operator++ ()
istream_iterator<T, Distance> operator++ (int)
Retrieve the next element from the input stream.
bool
operator== (const istream_iterator<T, Distance>& x,
const istream_iterator<T, Distance>& y)
Equality operator. Returns true if x is the same as y.
//
// io_iter.cpp
//
#include <iterator>
#include <vector>
#include <numeric>
#include <iostream.h>
int main ()
{
vector<int> d;
int total = 0;
//
// Collect values from cin until end of file
// Note use of default constructor to get ending iterator
//
cout << "Enter a sequence of integers (eof to quit): " ;
copy(istream_iterator<int,vector<int>::difference_type>(cin),
istream_iterator<int,vector<int>::difference_type>(),
inserter(d,d.begin()));
//
// stream the whole vector and the sum to cout
//
copy(d.begin(),d.end()-1,ostream_iterator<int>(cout," + "));
if (d.size())
cout << *(d.end()-1) << " = " <<
accumulate(d.begin(),d.end(),total) << endl;
return 0;
}
If your compiler does not support default template parameters, then you will need to always supply the Allocator template argument. For instance, you'll have to write :
vector<int, allocator>
instead of :
vector<int>