Halting problem ? Ha!

C++'s template expander is modelled on ML's pattern matching. Cayenne and 
Qi are both perhaps two generations beyond that (both type systems being 
more powerful than Haskell's) in different directions: personally I prefer 
Qi's, but part of that is probably because it's possible to bootstrap the 
Qi implementation without being an ultra-guru).

Of course, C++ compilers often *appear* to not halt when compiling 
anyway ;}