Exact Discrete pseudo-Random Sampling

[Albert Chan]

For random number with small range (say, dice games), bit-mask is simple, and fast.
see O'Neill's benchmark, Efficiently Generating a Number in a Range

lua> mt19937 = require 'mt19937' -- Mersenne Twister PRNG
lua> rand = mt19937.new(os.clock())
lua> dice = ('%010o'):format(rand(0, 2^30-1))
lua> dice                                      -- upto 10 valid dice throws !
3746210703
lua> dice = dice:gsub('[07]', '')      -- remove invalid throws
lua> dice
346213