SICP exercise solution in Groovy

Exercise 1.11.  A function f is defined by the rule that f(n) = n if n<3 and f(n) = f(n - 1) + 2f(n - 2) + 3f(n -
3) if n> 3. Write a procedure that computes f by means of a recursive process. Write a procedure that
computes f by means of an iterative process.

def frec(n) {
    if (n<3) return n;
    return 3*frec(n-1) + 2*frec(n-2) + frec(n-3);
}

def fite(n) {
    def fite_impl;
    fite_impl = { m, t, arr ->
        if (m == t) return arr[2];
        if (m > t) return arr[t];
        return fite_impl(m+1, t,
            [arr[1], arr[2], arr[0] + 2*arr[1] + 3*arr[2]]);
    }
    fite_impl(2, n, [0, 1, 2]);
}

println "${frec(4)}, ${fite(4)}"
println "${frec(3)}, ${fite(3)}"
println "${frec(2)}, ${fite(2)}"
println "${frec(1)}, ${fite(1)}"
println "${frec(0)}, ${fite(0)}"