rand [[<min>] <max>]
This returns a random floating-point number. With no arguments, the number will be uniformly distributed in the range [0.0,1.0). With one argument, the number will be in the range [0.0, max). With two arguments, the number will be in the range [min, max).
This uses the same generator that Lens uses for its internal random real numbers. Therefore, calling this will affect the next value used during weight randomization, building sparse projections, or in other randomized procedures.