Q: How to choose from a fixed set of random values?

[dcastro]

(If this is not the proper channel for questions, please close this and kindly point me to the right channel)

Say I want to generate some value v from a fixed set of random integers. E.g.

case class Person(age: Int)

val personRng = f(Rng.int, Rng.int, Rng.int).map(i => Person(i))

val io = personRng.run

io.unsafePerformIO // prints `Person(10)`
io.unsafePerformIO // prints `Person(19)`
io.unsafePerformIO // prints `Person(10)`
io.unsafePerformIO // prints `Person(19)`
io.unsafePerformIO // prints `Person(77)`
io.unsafePerformIO // prints `Person(19)`
io.unsafePerformIO // prints `Person(77)`

I don't care what the numbers are, but I care that they're always picked from a pool with a fixed size.

I tried the following, which did not produce what I expected:

val personRng = for {
  a <- Rng.int
  b <- Rng.int
  c <- Rng.int
  age <- Rng.oneof(a, b, c)
} yield Person(age)

This seems like it should be easy to achieve, but I can't figure out how.

Thanks in advance.