Creating Libraries Callable from C

[TJB via Digitalmars-d-learn]

Is it possible to write a library that is callable from C without 
the enduser even knowing it was written in D? That is, can a C 
programmer use the library as though it were written in C 
straightforwardly? Or for that matter, by an enduser programming 
in Python or Lua where the library is being exposed through those 
languages' C API?

I'm sure this is a widely discussed and well understood topic, 
but I am a newbie (and have no formal training in CS) and don't 
know where to look for documentation.

A little baby tutorial would be super helpful and well received 
by this newbie.

Thanks so much!

TJB