lib/Hcompta/Lib/NonEmpty.hs

   1 module Hcompta.Lib.NonEmpty where
   2
   3 import qualified Data.List
   4 -- import qualified Data.List.NonEmpty as NonEmpty
   5 import           Data.List.NonEmpty (NonEmpty(..))
   6 import           Data.Monoid ((<>))
   7
   8
   9 -- | Return the given 'NonEmpty' without its last section if any.
  10 ascending :: NonEmpty x -> Maybe (NonEmpty x)
  11 ascending (_:|[]) = Nothing
  12 ascending (x:|xs) = Just (x:|Data.List.init xs)
  13 {-# INLINE ascending #-}
  14
  15 -- | Return all the prefixes of the given 'NonEmpty' (including itself).
  16 prefixes :: NonEmpty x -> [NonEmpty x]
  17 prefixes (y:|ys) = go y [] ys []
  18         where
  19                 go :: x -> [x] -> [x] -> [NonEmpty x] -> [NonEmpty x]
  20                 go x0 s []     = (:) (x0:|s)
  21                 go x0 s (x:xs) = go x0 (s <> [x]) xs . (:) (x0:|s)