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|
{-# LANGUAGE Trustworthy #-}
{-# LANGUAGE NoImplicitPrelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : Data.List
-- Copyright : (c) The University of Glasgow 2001
-- License : BSD-style (see the file libraries/base/LICENSE)
--
-- Maintainer : libraries@haskell.org
-- Stability : stable
-- Portability : portable
--
-- Operations on lists.
--
-----------------------------------------------------------------------------
module Data.List
(
-- * Basic functions
(++)
, head
, last
, tail
, init
, uncons
, singleton
, 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
, 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' ('Prelude.compare'
-- ``Data.Function.on`` 'Prelude.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
--
-- >>> isSubsequenceOf "GHC" "The Glorious Haskell Compiler"
-- True
-- >>> isSubsequenceOf ['a','d'..'z'] ['a'..'z']
-- True
-- >>> isSubsequenceOf [1..10] [10,9..0]
-- False
--
-- For the result to be 'True', the first list must be finite;
-- for the result to be 'False', the second list must be finite:
--
-- >>> [0,2..10] `isSubsequenceOf` [0..]
-- True
-- >>> [0..] `isSubsequenceOf` [0,2..10]
-- False
-- >>> [0,2..] `isSubsequenceOf` [0..]
-- * Hangs forever*
--
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
|
