rnd

Definition: atom x2 = rnd()
Description: Returns a random floating point number in the range 0.0 to 1.0 inclusive.
Comments: In order to get reproducible results from this function, you should call set_rand() with a reproducible value prior to calling this.

You should note that the implementation is trivial (see builtins/VM/prnd.e) and you should not assume that the results will be perfectly distributed or cryptographically secure. Many other random number generators can be found in the RDS Eu archive, let me know of any that you think should be included in the standard distribution.
Example:
set_rand(1001)
s = rnd() -- s is 0.4817850515
See Also: set_rand