moduleNumeric.Probability.Example.DicewhereimportqualifiedNumeric.Probability.Distribution asDistimportNumeric.Probability.Distribution ((?? ),)importControl.Monad(liftM2,replicateM)typeDie =InttypeProbability =RationaltypeDist =Dist.T Probability die::Dist Die die =Dist.uniform [1..6]-- | product of independent distributionstwoDice::Dist (Die ,Die )twoDice =liftM2(,)die die dice::Int->Dist [Die ]dice =flipreplicateMdie twoSixes::Probability twoSixes =(==(6,6))?? twoDice {- |
@sixes p n@ computes the probability of getting
p sixes (@>1@, @==2@, ...) when rolling n dice
-}sixes::(Int->Bool)->Int->Probability sixes p n =(p .length.filter(==6))?? dice n droll::Dist Die droll =liftM2(+)(Dist.uniform [0,1])die g3::Probability g3 =(>3)?? die addTwo::Dist Die addTwo =liftM2(+)die die