Boost
C++ Libraries
...one of the most highly
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— Herb Sutter and Andrei
Alexandrescu, C++
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boost::accumulators::tag::external<Feature, Tag, void>
// In header: <boost/accumulators/framework/accumulators/external_accumulator.hpp> template<typename Feature, typename Tag> struct external<Feature, Tag, void> : public boost::accumulators::depends_on< reference< void, Tag > >, public boost::accumulators::depends_on<> { // types typedef unspecified impl; typedef unspecified impl; };