std::istream_iterator
Defined in header <iterator>
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template< class T, class CharT = char, |
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std::istream_iterator is a single-pass input iterator that reads successive objects of type T from the std::basic_istream object for which it was constructed, by calling the appropriate operator>>. The actual read operation is performed when the iterator is incremented, not when it is dereferenced. The first object may be read when the iterator is constructed or when the first dereferencing is done. Otherwise, dereferencing only returns a copy of the most recently read object.
The default-constructed std::istream_iterator is known as the end-of-stream iterator. When a valid std::istream_iterator reaches the end of the underlying stream, it becomes equal to the end-of-stream iterator. Dereferencing or incrementing it further invokes undefined behavior.
A typical implementation of std::istream_iterator holds two data members: a pointer to the associated std::basic_istream object and the most recently read value of type T.
When reading characters, std::istreambuf_iterator is more efficient, since it avoids the overhead of constructing and destructing the sentry object once per character.
Contents |
[edit] Member types
Member type | Definition |
char_type | CharT |
traits_type | Traits |
istream_type | std::basic_istream<CharT, Traits> |
[edit] Member functions
constructs a new istream_iterator (public member function) | |
(destructor) (implicitly declared) |
destructs an istream_iterator, including the cached value (public member function) |
obtains a copy of the current element accesses a member of the current element (public member function) | |
advances the istream_iterator (public member function) |
[edit] Non-member functions
compares two istream_iterators (function template) |
Inherited from std::iterator
Member types
Member type | Definition |
value_type | T |
difference_type | Distance |
pointer | const T* |
reference | const T& |
iterator_category | std::input_iterator_tag |
[edit] Example
#include <iostream> #include <sstream> #include <iterator> #include <algorithm> int main() { std::istringstream str("0.1 0.2 0.3 0.4"); std::partial_sum( std::istream_iterator<double>(str), std::istream_iterator<double>(), std::ostream_iterator<double>(std::cout, " ")); }
Output:
0.1 0.3 0.6 1
[edit] See also
output iterator that writes to std::basic_ostream (class template) | |
input iterator that reads from std::basic_streambuf (class template) |