ZoKrates supports code that is generic over constants of the u32 type. No specific keyword is used: the compiler determines if the generic parameters are indeed constant at compile time. Here's an example of generic code in ZoKrates:

def sum<N>(field[N] a) -> field {
    field mut res = 0;
    for u32 i in 0..N {
        res = res + a[i];
    return res;

def main(field[3] a) -> field {
    return sum(a);