-- | Common 'Control.Monad' variations.
module Sound.SC3.Common.Monad where

import Control.Monad {- base -}

-- | 'sequence' of 'repeat'
repeatM :: Monad m => m t -> m [t]
repeatM = sequence . repeat

-- | 'void' of 'repeatM'.
repeatM_ :: Monad m => m t -> m ()
repeatM_ = void . repeatM

-- | 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 = foldr (<=<) return

-- | 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)