Version: 2.x

Random

Random service provides utilities to generate random numbers. It's a functional wrapper of scala.util.Random. This service contains various different pseudo-random generators like nextInt, nextBoolean and nextDouble. Each random number generator functions return a URIO[Random, T] value.

import zio._

for {
  randomInt    <- Random.nextInt
  _            <- Console.printLine(s"A random Int: $randomInt")
  randomChar   <- Random.nextPrintableChar
  _            <- Console.printLine(s"A random Char: $randomChar")
  randomDouble <- Random.nextDoubleBetween(1.0, 5.0)
  _            <- Console.printLine(s"A random double between 1.0 and 5.0: $randomDouble")
} yield ()

Random service has a setSeed which helps us to alter the state of the random generator. It is useful for setting up a test version of Random service when we need to reproduce always the same sequence of numbers.

import zio._

for {
  _        <- Random.setSeed(0)
  nextInts <- (Random.nextInt zip Random.nextInt)
} yield assert(nextInts == (-1155484576,-723955400))

Also, it has a utility to shuffle a list and to generate random samples from Gaussian distribution:

shuffle - Takes a list as an input and shuffles it.
nextGaussian — Returns the next pseudorandom, Gaussian ("normally") distributed double value with mean 0.0 and standard deviation 1.0.

Note:

Random numbers that are generated via Random service are not cryptographically strong. Therefore it's not safe to use the ZIO Random service for security domains where a high level of security and randomness is required, such as password generation.

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