Name: game-probability
Version: 1.0
Synopsis: Simple probability library for dice rolls and similar simple games of chance
-- A longer description of the package.
Description: A library designed to aid in easily calculating the
probability of various outcomes of dice rolls. The
central types are held in the
"Numeric.Probability.Game.Event" module, the dice are
defined in the "Numeric.Probability.Game.Dice" module,
and the functions for calculating probabilities are in
the "Numeric.Probability.Game.Query" module. Various
examples are scattered throughout the library, but here
are some more:
.
Evalulates the chance of a coin toss turning up heads:
.
> chanceTrue coinToss
.
Shows the chances of each outcome of rolling two six-sided dice, as a textual bar chart:
.
> show (2*d6)
.
The chance of getting an 18 when rolling 3 six-sided dice and rerolling on any total less than 8:
.
> chancePred (== 18) ((3*d6) `rerollOn` [3..7])
.
As a more complex example, this implements my memory/understanding of the original
World of Darkness dice system
().
You roll a given number of 10-sided dice, rolling one
extra for every 10 you score if you are specialised. The number of 1s on the
original roll are subtracted from the total number of
dice that equal or exceed the difficulty target:
.
> successes :: Int -> Int -> Bool -> EventM Int
> successes target dice specialised
> = do initial <- replicateM dice d10
> extra <- if specialised
> then replicateM (count (== 10) initial) d10
> else return []
> return (count (>= target) (initial ++ extra) - count (== 1) initial)
> where
> count f xs = length (filter f xs)
.
If only all RPGs specified their rules in Haskell!
.
See also the blog post on the design of the library:
License: BSD3
License-file: LICENSE
Author: Neil Brown
Maintainer: neil@twistedsquare.com
-- Copyright:
Category: Math
Build-type: Simple
Cabal-version: >=1.6
Library
-- Modules exported by the library.
Exposed-modules: Numeric.Probability.Game.Event
Numeric.Probability.Game.Dice
Numeric.Probability.Game.Query
-- Packages needed in order to build this package.
Build-depends: base >= 4 && < 5, probability == 0.2.*, random == 1.0.*
Extensions: GeneralizedNewtypeDeriving FlexibleInstances
GHC-Options: -Wall