doc/guide/src/MLtonRandom.adoc

   1 MLtonRandom
   2 ===========
   3
   4 [source,sml]
   5 ----
   6 signature MLTON_RANDOM =
   7    sig
   8       val alphaNumChar: unit -> char
   9       val alphaNumString: int -> string
  10       val rand: unit -> word
  11       val seed: unit -> word option
  12       val srand: word -> unit
  13       val useed: unit -> word option
  14    end
  15 ----
  16
  17 * `alphaNumChar ()`
  18 +
  19 returns a random alphanumeric character.
  20
  21 * `alphaNumString n`
  22 +
  23 returns a string of length `n` of random alphanumeric characters.
  24
  25 * `rand ()`
  26 +
  27 returns the next pseudo-random number.
  28
  29 * `seed ()`
  30 +
  31 returns a random word from `/dev/random`.  Useful as an arg to
  32 `srand`.  If `/dev/random` can not be read from, `seed ()` returns
  33 `NONE`.  A call to `seed` may block until enough random bits are
  34 available.
  35
  36 * `srand w`
  37 +
  38 sets the seed used by `rand` to `w`.
  39
  40 * `useed ()`
  41 +
  42 returns a random word from `/dev/urandom`.  Useful as an arg to
  43 `srand`.  If `/dev/urandom` can not be read from, `useed ()` returns
  44 `NONE`.  A call to `useed` will never block -- it will instead return
  45 lower quality random bits.