{-# LANGUAGE Trustworthy #-} {-# LANGUAGE NoImplicitPrelude #-} ----------------------------------------------------------------------------- -- | -- Module : Data.List -- Copyright : (c) The University of Glasgow 2001 -- License : BSD-style (see the file libraries/base/LICENSE) -- -- Maintainer : [email protected] -- Stability : stable -- Portability : portable -- -- Operations on lists. -- ----------------------------------------------------------------------------- module Data.List ( -- * Basic functions (++) , head , last , tail , init , uncons , null , length -- * List transformations , map , reverse , intersperse , intercalate , transpose , subsequences , permutations -- * Reducing lists (folds) , foldl , foldl' , foldl1 , foldl1' , foldr , foldr1 -- ** Special folds , concat , concatMap , and , or , any , all , sum , product , maximum , minimum -- * Building lists -- ** Scans , scanl , scanl' , scanl1 , scanr , scanr1 -- ** Accumulating maps , mapAccumL , mapAccumR -- ** Infinite lists , iterate , repeat , replicate , cycle -- ** Unfolding , unfoldr -- * Sublists -- ** Extracting sublists , take , drop , splitAt , takeWhile , dropWhile , dropWhileEnd , span , break , stripPrefix , group , inits , tails -- ** Predicates , isPrefixOf , isSuffixOf , isInfixOf , isSubsequenceOf -- * Searching lists -- ** Searching by equality , elem , notElem , lookup -- ** Searching with a predicate , find , filter , partition -- * Indexing lists -- | These functions treat a list @xs@ as a indexed collection, -- with indices ranging from 0 to @'length' xs - 1@. , (!!) , elemIndex , elemIndices , findIndex , findIndices -- * Zipping and unzipping lists , zip , zip3 , zip4, zip5, zip6, zip7 , zipWith , zipWith3 , zipWith4, zipWith5, zipWith6, zipWith7 , unzip , unzip3 , unzip4, unzip5, unzip6, unzip7 -- * Special lists -- ** Functions on strings , lines , words , unlines , unwords -- ** \"Set\" operations , nub , delete , (\\) , union , intersect -- ** Ordered lists , sort , sortOn , insert -- * Generalized functions -- ** The \"@By@\" operations -- | By convention, overloaded functions have a non-overloaded -- counterpart whose name is suffixed with \`@By@\'. -- -- It is often convenient to use these functions together with -- 'Data.Function.on', for instance @'sortBy' ('compare' -- \`on\` 'fst')@. -- *** User-supplied equality (replacing an @Eq@ context) -- | The predicate is assumed to define an equivalence. , nubBy , deleteBy , deleteFirstsBy , unionBy , intersectBy , groupBy -- *** User-supplied comparison (replacing an @Ord@ context) -- | The function is assumed to define a total ordering. , sortBy , insertBy , maximumBy , minimumBy -- ** The \"@generic@\" operations -- | The prefix \`@generic@\' indicates an overloaded function that -- is a generalized version of a "Prelude" function. , genericLength , genericTake , genericDrop , genericSplitAt , genericIndex , genericReplicate ) where import Data.Foldable import Data.Traversable import Data.OldList hiding ( all, and, any, concat, concatMap, elem, find, foldl, foldl1, foldl', foldr, foldr1, mapAccumL, mapAccumR, maximum, maximumBy, minimum, minimumBy, length, notElem, null, or, product, sum ) import GHC.Base ( Bool(..), Eq((==)), otherwise ) -- | The 'isSubsequenceOf' function takes two lists and returns 'True' if all -- the elements of the first list occur, in order, in the second. The -- elements do not have to occur consecutively. -- -- @'isSubsequenceOf' x y@ is equivalent to @'elem' x ('subsequences' y)@. -- -- @since 4.8.0.0 -- -- ==== __Examples__ -- -- >>> isSubsequenceOf "GHC" "The Glorious Haskell Compiler" -- True -- >>> isSubsequenceOf ['a','d'..'z'] ['a'..'z'] -- True -- >>> isSubsequenceOf [1..10] [10,9..0] -- False isSubsequenceOf :: (Eq a) => [a] -> [a] -> Bool isSubsequenceOf [] _ = True isSubsequenceOf _ [] = False isSubsequenceOf a@(x:a') (y:b) | x == y = isSubsequenceOf a' b | otherwise = isSubsequenceOf a b