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 res = 0
    for u32 i in 0..N do
        res = res + a[i]
    return res

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