Game.LambdaHack.Random

Representation of probabilities and random computations.

The Rng monad

type Rnd a = State StdGen a

The monad of computations with random generator state.

Random operations

randomR :: Random a => (a, a) -> Rnd a

Get a random object within a range with a uniform distribution.

oneOf :: [a] -> Rnd a

Get any element of a list with equal probability.

frequency :: Show a => Frequency a -> Rnd a

Gen an element according to a frequency distribution.

roll :: Int -> Rnd Int

Roll a single die.

Rolling dice

data RollDice

Dice: 1d7, 3d3, 1d0, etc. RollDice a b represents a rolls of b-sided die.

Constructors

RollDice Word8 Word8

Instances

Eq RollDice

Ord RollDice

Read RollDice

Show RollDice

rollDice :: RollDice -> Rnd Int

Roll dice and sum the results.

maxDice :: RollDice -> Int

Maximal value of dice.

minDice :: RollDice -> Int

Minimal value of dice.

meanDice :: RollDice -> Rational

Mean value of dice.

Rolling 2D coordinates

data RollDiceXY

Dice for rolling a pair of integer parameters pertaining to, respectively, the X and Y cartesian 2D coordinates.

Constructors

RollDiceXY (RollDice, RollDice)

Instances

Show RollDiceXY

rollDiceXY :: RollDiceXY -> Rnd (Int, Int)

Roll the two sets of dice.

Rolling dependent on depth

type RollDeep = (RollDice, RollDice)

Dice for parameters scaled with current level depth. To the result of rolling the first set of dice we add the second, scaled in proportion to current depth divided by maximal dungeon depth.

rollDeep :: Int -> Int -> RollDeep -> Rnd Int

Roll dice scaled with current level depth. Note that at the first level, the scaled dice are always ignored.

chanceDeep :: Int -> Int -> RollDeep -> Rnd Bool

Roll dice scaled with current level depth and return True if the results if greater than 50.

intToDeep :: Int -> RollDeep

Generate a RollDeep that always gives a constant integer.

maxDeep :: RollDeep -> Int

Maximal value of scaled dice.

Fractional chance

type Chance = Rational

Fractional chance.

chance :: Chance -> Rnd Bool

Give True, with probability determined by the fraction.