work around stack overflow error when going through recursive function 300+ times in groovy?

I have the following code, trying to find the first number of the Fibonacci sequence with over 1000 digits:

z = 0g
def fib
fib = {a,b-> 
    if(a <= 10g**1000){
        z++ 
        fib(b.toBigInteger(), (a+b).toBigInt开发者_运维技巧eger())
    }else{
        return z
    }
}

fib(1,2)

This function works when I change "1000" to ~300 or less, and it computes in well under a half a second.

However, when I raise the variable above that, I get a stack overflow. I saw another question about this and the answer was to use a function called "doall," but I don't see that in Groovy.

I figure the solution is pretty simple at this point, but I don't know where to look for it...

Can anyone help me out?

Thanks so much!

---

If you are using Groovy 1.8, this is what the trampoline() method was designed to handle on Closures.

http://mrhaki.blogspot.com/2011/04/groovy-goodness-recursion-with-closure.html