Random Number Generation

This library provides a simple interface for generating random numbers and for other simple randomized operations, such as shuffling an array.

Basic Usage

To generate a random integer between 1 and 6, the following can be used.

(* Initialize once at the beginning of your program. *)
val _ = Mlrandom.init ()

fun rollD6 () = Mlrandom.uniformInt (1, 7)
val _ = print (Int.toString (rollD6 ()) ^ "\n")

This results in output like

3

To shuffle an array, the following can be used.

structure A = ArrayToString(type t = int; val toString = Int.toString)

(* Initialize once at the beginning of your program. *)
val _ = Mlrandom.init ()

val data = Array.fromList [1,2,3,4,5]
val _ = print ("Before: " ^ A.toString data ^ "\n")

val _ = Mlrandom.shuffle data
val _ = print ("After: " ^ A.toString data ^ "\n")

This results output like

Before: Array.fromList [1,2,3,4,5]
After: Array.fromList [3,2,1,5,4]

Interface

• val init : unit -> unit
• val rand : unit -> int
• val uniformInt : (int * int) -> int
• val uniformReal : (real * real) -> real
• val shuffle : 'a array -> unit

Method Overview

• init ()
  • Initialize the random number generator with a random seed. Skipping this call with result in deterministic behavior, which may be useful for testing.
• uniformInt (l, h)
  • Return an integer in range [l, h).
• uniformReal (l, h)
  • Return a real number in range [l, h).
• rand ()
  • Return a random integer.
• shuffle arr
  • Shuffles arr in-place using the Fisher-Yates algorithm.