-- | Functions to make writing 'Applicative' and 'Monad' UGen graphs
-- less clumsy.
module Sound.SC3.Monad.Syntax where

import Control.Applicative {- base -}
import Control.Monad {- base -}

infixl 7  .*,*.,.*.
infixl 6  .+,+.,.+.

-- | '+' variant with 'Functor' at left.
--
-- > fmap (== 5) (return 3 .+ 2)
(.+) :: (Functor f, Num a) => f a -> a -> f a
m .+ n = fmap (+ n) m

-- | '+' variant with 'Functor' at right.
--
-- > fmap (== 5) (3 +. return 2)
(+.) :: (Functor f, Num a) => a -> f a -> f a
m +. n = fmap (+ m) n

-- | '+' variant with 'Applicative' at left and right.
--
-- > fmap (== 5) (return 3 .+. return 2)
(.+.) :: (Applicative m, Num a) => m a -> m a -> m a
(.+.) = liftA2 (+)

-- | '*' variant with 'Functor' at left.
--
-- > fmap (== 6) (return 3 .* 2)
(.*) :: (Functor f, Num a) => f a -> a -> f a
m .* n = fmap (* n) m

-- | '*' variant with 'Functor' at right.
--
-- > fmap (== 6) (3 *. return 2)
(*.) :: (Functor f, Num a) => a -> f a -> f a
m *. n = fmap (* m) n

-- | '*' variant with 'Applicative' at left and right.
--
-- > fmap (== 6) (return 3 .*. return 2)
(.*.) :: (Applicative m, Num a) => m a -> m a -> m a
(.*.) = liftA2 (*)

-- | Right to left compositon of 'Monad' functions.
--
-- > fmap (== 7) (composeM [return . (+ 1),return . (* 2)] 3)
-- > fmap (== 8) (composeM [return . (* 2),return . (+ 1)] 3)
composeM :: Monad m => [a -> m a] -> a -> m a
composeM f = foldr (<=<) return f

-- | Feed forward composition of /n/ applications of /f/.
--
-- > fmap (== 3) (chainM 3 (return . (+ 1)) 0)
chainM :: Monad m => Int -> (b -> m b) -> b -> m b
chainM n f = foldr (<=<) return (replicate n f)