Boost C++ Application Development Cookbook - Second Edition

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There is one fundamental difference between boost::fusion::for_each and std::for_each. The std::for_each function contains a loop inside it and determinates at runtime, how many iterations must be done. However, boost::fusion::for_each() knows iterations count at compile time and fully unrolls the loop. For the boost::tuple<cat, int, std::string> tup2, the boost::fusion::for_each(tup2, functor) call is equivalent to the following code:

    functor(boost::fusion::at_c<0>(tup2));    functor(boost::fusion::at_c<1>(tup2));    functor(boost::fusion::at_c<2>(tup2));

C++11 contains no Boost.Fusion classes. All the methods of Boost.Fusion are very effective. They do as much as possible at compile time and have some very advanced optimizations. ...