* Problem - I have the following types "uint8, uint16, uint32, int8, int16, int32, float32, float64" called "scalar types". - The types "uint8, uint16, uint32" are called "size types". - "List types" are defined as every possible combination of size types and scalar types (24 in this case). - For every scalar type and every size type I need to store a callback. - The function templates template <typename ScalarType> void scalar_type_callback(); template <typename SizeType, typename ScalarType> void list_type_callback(); are function templates and not functions, and cannot be stored in a function object. * Solution 1 I wrote code using boost::mpl (a time ago, with some help of the boost groups) that generates a class containing a callback for each scalar type and a class containing a callback for each list type. * Solution 2 The code from solution 1 worked, but was slow to compile, and I did not fully understand it. Therefore I decided to read the book "C++ Template Metaprogramming" and reimplement the code from scratch, without boost::mpl. The attached code consists of - A number number of simple mpl constructs similar to the ones in boost::mpl (bool_, if_, eval_if, pair, inherit, identity, void_). - A single sequence list with operations push_front and reverse. It does not include an abstraction layer over sequences. - A number of simple mpl constructs needed to implement the solution to the problem above (for_each, joint_view, transform, product_view, inherit_linearly). Since sequences are not abstracted, these are implemented in terms of the list sequence and (only) the two operations push_front and reverse, using fold-like constructs. The only construct not in boost::mpl is product_view, which constructs the outer product of two sequences (it might be interesting to include something like this in boost::mpl). There is no support for lambda expressions, which causes some complications (e.g. the Operation argument for transform is a class template in my design), but the mpl code is pretty clear and usable. I am attaching this code in the hope it is usefull to anyone (e.g. didactical purposes, small mpl systems without using boost::mpl). I am also open to suggestions for improvements, simplifications, ... -- Ares Lagae Computer Graphics Research Group, Katholieke Universiteit Leuven http://www.cs.kuleuven.be/~ares/