So, I finally found some time for a Template Metaranting follow-up post. This time let's get down to business as this one contains a fair amount of code.

Sadly, I won't rant as much but instead I'll try to show how awesome D's templates really are. We'll write a piece of code, based on this Scheme implementation, that is, a simple monad) that we'll use to build a binary tree, with uniquely numbered nodes containing their height, without any global state (therefore purely) entirely at compile time.

Here's another post in the series, this time it's C++ vs. the D programming language.

Let's talk about templates. If you've ever tried templates in C++ you surely as hell recall the pages and PAGES of compiler errors and seemingly random placement of typename keyword. Trust me, there are EVEN WORSE problems with templates in C++... Consider the following:

struct Foo {
  template<int N>
  void bar() {}

  template<int N>
  struct Bar {};
};

template<typename T>
void f() {
  T foo;
  foo.template bar<0>();         // Line 12
  typename T::template Bar<0> b; // Line 13
}

int main() {
  f<Foo>();
}