The rand built-in function has the form:
fun rand = (uint<32> seed = 0) int<32>:
It returns a pseudo-random number in the range of the unsigned 32-bit integers. If a seed different to zero is provided, it is used to initialize a new sequence of pseudo-random numbers (which includes the one returned.)
The gettime builtin function can be used in order to seed the
pseudo-random number generator very easily:
srand (gettime[1])