Johan, there is an mpl::for_each construct to do this. Unfortunately for_each is not documented, but it is a part of mpl library. If you have the MPL book from Dave and Alexey you can read about it on page 175. On page 176-179 you will find 3 differnt examples about type printing. Below is one of the approaches converted to you example: Your example should work with the following sample: #include <iostreams> #include <boost/mpl/for_each.hpp> #include <boost/mpl/placeholders.hpp> namespace mpl = boost::mpl; template<class T> struct Type2Type {}; //this will prevent instantiation of every type // and transport the type information only // => Type2Type is only 1 byte big => cheaper as a reference or ptr struct WriteSize { template<class T> void operator() (Type2Type<T> t) { std::cout << sizeof(T) << " "; } }; typedef mpl::vector<float,double,long double> SomeVector; //now the call to for_each mpl::for_each<SomeVector, Type2Type<mpl::_1> >(WriteSize()); With Kind Regards, Ovanes Markarian On Thu, January 4, 2007 11:34, Johan Torp wrote:

I would like to generate one call to a templated function for each type in an MPL sequence. Which is the best way to do this? E.g.:

typedef vector<float,double,long double> SomeVector; template <typename T> write_size() { std::cout << sizeof(T) << " "; }

Should somehow expand to:

write_size<float>(); write_size<double>(); write_size<long double>();

I have managed to do this "manually" in a fairly general way, what I'm looking for is some part of boost which replaces my ForEach struct below or some nicer way of writing the same code:

============================================== struct WriteSize { template<typename T> void Call() {write_size<T>();} };

template <class It, class End> struct ForEach { template <class Func> static void Call(Func& func) { func.Call<typename It::type>(); ForEach<typename next<It>::type, End>::Call(func); } };

template <class End> struct ForEach<End, End> { template <class Func> static void Call(Func&) {} };

// Then I can generate the calls by WriteSize ws; ForEach<begin<SomeVector;>::type, end<SomeVector;>::type>::Call(ws);

==============================================

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