[emersonrsantos]

In Forth language would be:

  : fib 2dup + ;

2dup word duplicates n and n-1 elements and put it on the top of the stack.

+ word takes n and n-1 elements from the stack and sum them. The result goes on top of the stack.

Just start with 1 and 1 at the top of stack.

[willvk]

That's some very concise code golf! It would be interesting in seeing how Forth compiles this under the hood.

[pjc50]

Normally Forth is interpreted. Compiled Forth code is unlikely to look particularly clean or elegant.

(If you like languages with a very high density of functionality to symbol count, you should look at APL and its successor J)