Fibonacci sequence using recursion in the Groovy language.

Fibonacci.groovy

def fib(n) {
    switch (n) {
        case 0: 0; break
        case 1..2: 1; break
        default: n = fib(n-1) + fib(n-2); break
    }
}
assert [0,1,1,2,3,5,8,13,21,34,55,89,144,233,377,610,987] == (0..16).collect {fib(it)}