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module Data.Sv.Alien.Containers (intersperseSeq) where

import Control.Applicative ((<**>))
import Data.Sequence (Seq, ViewL (EmptyL, (:<)), viewl, (<|), singleton, empty)

-- Added in containers 0.5.8, but we duplicate it here to support
-- older versions, including 0.5.6.2, which is a GHC boot library for
-- GHC 7.10
intersperseSeq :: a -> Seq a -> Seq a
intersperseSeq y xs = case viewl xs of
  EmptyL -> empty
  p :< ps -> p <| (ps <**> (pure y <| singleton id))