Hi Julia community,

I am using Julia for my economics research and this is my first question posted here. Hopefully it is a simple one that more experienced users can easily answer.

I am trying to use automatic differentiation to compute the derivative of the two functions below.

```
function simplefunction_v1(x)
T = 3
temp = x.^(0:T)
return temp
end
function simplefunction_v2(x)
T = 3
temp = zeros(T+1)
temp[1] = 1.0
temp[2] = x
for iT = 3:T+1
temp[iT] = x*temp[iT-1]
end
return temp
end
```

These two functions return equivalent results for a scalar x. I run the following to use the ForwardDiff package to calculate the derivative of each function evaluated at x=2.0.

```
using ForwardDiff
ForwardDiff.derivative(simplefunction_v1,2.0)
ForwardDiff.derivative(simplefunction_v2,2.0)
```

While the second line (simplefunction_v1) above works as expected, I get an error from running the third line (simplefunction_v2).

It goes without saying that my actual application is quite a bit more involved, where I cannot get rid of the recursive relationship in the function definition. I would greatly appreciate any direction as to how to get the second version of the function working with automatic differentiation.

Thanks a lot.