Metaprogramming in C++ and in D

Question

The template mechanism in C++ only accidentally became useful for template metaprogramming. On the other hand, D\'s was designed specifically to facilitate this. And apparently

Answer 1

The best examples of D metaprogramming are D standard library modules that make heavy use of it vs. C++ Boost and STL modules. Check out D's std.range, std.algorithm, std.functional and std.parallelism. None of these would be easy to implement in C++, at least with the kind of clean, expressive API that the D modules have.

The best way to learn D metaprogramming, IMHO, is by these kinds of examples. I learned largely by reading the code to std.algorithm and std.range, which were written by Andrei Alexandrescu (a C++ template metaprogramming guru who has become heavily involved with D). I then used what I learned and contributed the std.parallelism module.

Also note that D has compile time function evaluation (CTFE) which is similar to C++1x's constexpr but much more general in that a large and growing subset of functions that can be evaluated at runtime can be evaluated unmodified at compile time. This is useful for compile-time code generation, and the generated code can be compiled using string mixins.