Task

(Given an equal-probability generator of one of the integers 1 to 5
as dice5),   create dice7 that generates a pseudo-random integer from
1 to 7 in equal probability using only dice5 as a source of random
numbers,   and check the distribution for at least one million calls using the function created in   Simple Random Distribution Checker.


Implementation suggestion:
dice7 might call dice5 twice, re-call if four of the 25
combinations are given, otherwise split the other 21 combinations
into 7 groups of three, and return the group index from the rolls.

(Task adapted from an answer here)

import System.Random
import Data.List
 
sevenFrom5Dice = do
  d51 <- randomRIO(1,5) :: IO Int
  d52 <- randomRIO(1,5) :: IO Int
  let d7 = 5*d51+d52-6
  if d7 > 20 then sevenFrom5Dice
       else return $ 1 + d7 `mod` 7