Boost C++ Libraries

The I/O operators: << and >> work generically on all Fusion sequences. The I/O operators are overloaded in namespace boost::fusion ^[10]

The operator<< has been overloaded for generic output streams such that Sequence(s) are output by recursively calling operator<< for each element. Analogously, the global operator>> has been overloaded to extract Sequence(s) from generic input streams by recursively calling operator>> for each element.

Please note that, to display your adapted types via fusion IO system, corresponding overloaded operators should be introduced to same namespace of the type.

namespace your_awesome_library
{
    using boost::fusion::operators::operator>>; // for input
    using boost::fusion::operators::operator<<; // for output
    ...

The default delimiter between the elements is space, and the Sequence is enclosed in parenthesis. For Example:

vector<float, int, std::string> a(1.0f, 2, std::string("Howdy folks!");
cout << a;

outputs the vector as: (1.0 2 Howdy folks!)

The library defines three manipulators for changing the default behavior:

The argument to tuple_open, tuple_close and tuple_delimiter may be a char, wchar_t, a C-string, or a wide C-string.

Example:

std::cout << tuple_open('[') << tuple_close(']') << tuple_delimiter(", ") << a;

outputs the same vector, a as: [1.0, 2, Howdy folks!]

The same manipulators work with operator>> and istream as well. Suppose the std::cin stream contains the following data:

(1 2 3) [4:5]

The code:

vector<int, int, int> i;
vector<int, int> j;

std::cin >> i;
std::cin >> tuple_open('[') >> tuple_close(']') >> tuple_delimiter(':');
std::cin >> j;

reads the data into the vector(s) i and j.

Note that extracting Sequence(s) with std::string or C-style string elements does not generally work, since the streamed Sequence representation may not be unambiguously parseable.

Header

#include <boost/fusion/sequence/io.hpp>
#include <boost/fusion/include/io.hpp>