Rand

/// generate a random number between #start and #end (exclusive)
/// every time #clock updates. If start and end are not specified,
/// they default to 0.0 and 1.0
val rand: fn<'a: [Int, Float]>(?#start:'a, ?#end:'a, #clock:Any) -> 'a;

/// pick a random element from the array and return it. Update
/// each time the array updates. If the array is empty return
/// nothing.
val pick: fn(Array<'a>) -> 'a;

/// return a shuffled copy of a
val shuffle: fn(Array<'a>) -> Array<'a>;