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// Johnston notation tuning file for just intonation
// Accidentals for the 3-, 5-, 7- and 11-limit commas included

// 1. Reference note

C4: 440 * 3/5

// 2. Nominals - in Johnston system these are tuned 
// according to the Ptolemy tense diatonic scale
1/1 9/8 5/4 4/3 3/2 5/3 15/8 2/1

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Euterpea is a Haskell library for computer music (in terms of musical structures as well as lower-level audio signals.) The current instructions for the official project site specify how to carry out an installation using the build tool cabal, but you can also set up a stack project to work with Euterpea as an external dependency as well. Here's how I've been able to work with Euterpea in stack projects so far:

1. Create a stack project directory (here, I'll call mine example and use the simple template):

$ stack new example simple
$ cd example

2. I'd like to use Euterpea, so I'll add it to the build-depends section in my .cabal file:

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module IPv4 where 

import Control.Applicative ((<|>))
import Control.Monad.Combinators (count')
-- count' :: MonadPlus m => Int -> Int -> m a -> m [a]
-- count' m n p parses from m to n occurrences of p. 
-- If n is not positive or m > n, the parser equals to return []. 
-- Returns a list of parsed values.
import Data.Word (Word8, Word32)
import Text.Trifecta

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module Main where

import Text.Trifecta
import Control.Applicative ((<|>))

p1, p12, p123 :: Parser String
p1 = string "1"
p12 = string "12"
p123 = string "123"

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module Lib where

import Euterpea
import Data.Graph 
import Data.Array 
import System.Random       
import System.IO.Unsafe    (unsafeInterleaveIO, unsafePerformIO)
import Control.Monad       (liftM2, join)
import Control.Applicative (liftA2)

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-- | Filter a list with a predicate that produces an effect.
--
-- >>> filtering (ExactlyOne . even) (4 :. 5 :. 6 :. Nil)
-- ExactlyOne [4,6]
--
-- >>> filtering (\a -> if a > 13 then Empty else Full (a <= 7)) (4 :. 5 :. 6 :. Nil)
-- Full [4,5,6]
--
-- >>> filtering (\a -> if a > 13 then Empty else Full (a <= 7)) (4 :. 5 :. 6 :. 7 :. 8 :. 9 :. Nil)
-- Full [4,5,6,7]

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import Data.Graph 
import Data.Array 
import System.Random  
import Control.Monad ( liftM2 )

-- Given a graph       gr :: Graph ~ Array Vertex [Vertex]
-- and a vertex        v  :: Vertex
-- use System.Random, Data.Array functionality to specify 
-- a random walk (possibly non-terminating) within the graph.