3.17. kink/RAND¶

Provides pseudo random number generators using xorshift128+ algorithm, which is not cryptographically secure.

For details of xorshift128+, see the following paper:

http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf

To get a PRNG, call RAND.new with a seed number. RAND.new returns a PRNG fun.

The PRNG fun takes a positive int num as the exclusive Upper_bound, then returns a random int num in the range of [0, Upper_bound).

Example:

:RAND.require_from('kink/')

:new_coin <- {(:Seed)
  :rand = RAND.new(Seed)
  {()
    rand(2) % 2 == 0
  }
}

:flip_coin <- new_coin(42)
stdout.print_line(flip_coin.repr) # => true
stdout.print_line(flip_coin.repr) # => true
stdout.print_line(flip_coin.repr) # => false

The Seed is internally transformed to 127 bits, then used as the initial state of the PRNG.