As a non-C++ programmer with a background in functional programming, this similarity was a big surprise to me when I read a recent article on C++ template metaprogramming -- it's all basic functional programming techniques, with recursion, (kinda) pattern matching, etc. Very interesting!

I could see how mixing templates with other C++ paradigms could quickly get messy in the wrong hands, since it's very powerful.

Haskell did the same for me.