    -- File created: 2008-10-10 13:29:03

    {-# LANGUAGE CPP #-}

    module System.FilePath.Glob.Match (match, matchWith) where

    import Control.Exception (assert)
    import Data.Char         (isDigit, toLower, toUpper)
    import Data.List         (findIndex)
    import Data.Maybe        (fromMaybe, isJust)
    #if !MIN_VERSION_base(4,8,0)
    import Data.Monoid       (mappend)
    #endif
    import System.FilePath   (isPathSeparator, isExtSeparator)

    import System.FilePath.Glob.Base  ( Pattern(..), Token(..)
                                      , MatchOptions(..), matchDefault
                                      , isLiteral, tokToLower
                                      )
    import System.FilePath.Glob.Utils (dropLeadingZeroes, inRange, pathParts)

    -- |Matches the given 'Pattern' against the given 'FilePath', returning 'True'
    -- if the pattern matches and 'False' otherwise.
    match :: Pattern -> FilePath -> Bool
    match :: Pattern -> FilePath -> Bool
    match = MatchOptions -> Pattern -> FilePath -> Bool
    matchWith MatchOptions
    matchDefault

    -- |Like 'match', but applies the given 'MatchOptions' instead of the defaults.
    matchWith :: MatchOptions -> Pattern -> FilePath -> Bool
    matchWith :: MatchOptions -> Pattern -> FilePath -> Bool
    matchWith opts :: MatchOptions
    opts p :: Pattern
    p f :: FilePath
    f = MatchOptions -> [Token] -> FilePath -> Bool
    begMatch MatchOptions
    opts ([Token] -> [Token]
    lcPat ([Token] -> [Token]) -> [Token] -> [Token]
    forall a b. (a -> b) -> a -> b
    $ Pattern -> [Token]
    unPattern Pattern
    p) (FilePath -> FilePath
    lcPath FilePath
    f)
     where
       lcPath :: FilePath -> FilePath
    lcPath = if MatchOptions -> Bool
    ignoreCase MatchOptions
    opts then (Char -> Char) -> FilePath -> FilePath
    forall a b. (a -> b) -> [a] -> [b]
    map    Char -> Char
    toLower else FilePath -> FilePath
    forall a. a -> a
    id
       lcPat :: [Token] -> [Token]
    lcPat  = if MatchOptions -> Bool
    ignoreCase MatchOptions
    opts then (Token -> Token) -> [Token] -> [Token]
    forall a b. (a -> b) -> [a] -> [b]
    map Token -> Token
    tokToLower else [Token] -> [Token]
    forall a. a -> a
    id

    -- begMatch takes care of some things at the beginning of a pattern or after /:
    --    - . needs to be matched explicitly
    --    - ./foo is equivalent to foo (for any number of /)
    --
    -- .*/foo still needs to match ./foo though, and it won't match plain foo;
    -- special case that one
    --
    -- and .**/foo should /not/ match ../foo; more special casing
    --
    -- (All of the above is modulo options, of course)
    begMatch, match' :: MatchOptions -> [Token] -> FilePath -> Bool
    begMatch :: MatchOptions -> [Token] -> FilePath -> Bool
    begMatch _ (Literal '.' : AnyDirectory : _) (x :: Char
    x:y :: Char
    y:_)
       | Char -> Bool
    isExtSeparator Char
    x Bool -> Bool -> Bool
    && Char -> Bool
    isExtSeparator Char
    y = Bool
    False

    begMatch opts :: MatchOptions
    opts (Literal '.' : PathSeparator : pat :: [Token]
    pat) s :: FilePath
    s | MatchOptions -> Bool
    ignoreDotSlash MatchOptions
    opts =
       MatchOptions -> [Token] -> FilePath -> Bool
    begMatch MatchOptions
    opts ((Token -> Bool) -> [Token] -> [Token]
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile Token -> Bool
    isSlash [Token]
    pat) (FilePath -> FilePath
    dropDotSlash FilePath
    s)
     where
       isSlash :: Token -> Bool
    isSlash PathSeparator = Bool
    True
       isSlash _             = Bool
    False

       dropDotSlash :: FilePath -> FilePath
    dropDotSlash (x :: Char
    x:y :: Char
    y:ys :: FilePath
    ys) | Char -> Bool
    isExtSeparator Char
    x Bool -> Bool -> Bool
    && Char -> Bool
    isPathSeparator Char
    y =
          (Char -> Bool) -> FilePath -> FilePath
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile Char -> Bool
    isPathSeparator FilePath
    ys
       dropDotSlash xs :: FilePath
    xs = FilePath
    xs

    begMatch opts :: MatchOptions
    opts pat :: [Token]
    pat (x :: Char
    x:y :: Char
    y:s :: FilePath
    s)
       | Bool
    dotSlash Bool -> Bool -> Bool
    && Bool
    dotStarSlash        = MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    opts [Token]
    pat' FilePath
    s
       | MatchOptions -> Bool
    ignoreDotSlash MatchOptions
    opts Bool -> Bool -> Bool
    && Bool
    dotSlash =
            MatchOptions -> [Token] -> FilePath -> Bool
    begMatch MatchOptions
    opts [Token]
    pat ((Char -> Bool) -> FilePath -> FilePath
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile Char -> Bool
    isPathSeparator FilePath
    s)
     where
       dotSlash :: Bool
    dotSlash = Char -> Bool
    isExtSeparator Char
    x Bool -> Bool -> Bool
    && Char -> Bool
    isPathSeparator Char
    y
       (dotStarSlash :: Bool
    dotStarSlash, pat' :: [Token]
    pat') =
          case [Token]
    pat of
            Literal '.': AnyNonPathSeparator : PathSeparator : rest :: [Token]
    rest -> (Bool
    True, [Token]
    rest)
            _                                                       -> (Bool
    False, [Token]
    pat)

    begMatch opts :: MatchOptions
    opts pat :: [Token]
    pat (e :: Char
    e:_)
       | Char -> Bool
    isExtSeparator Char
    e
         Bool -> Bool -> Bool
    && Bool -> Bool
    not (MatchOptions -> Bool
    matchDotsImplicitly MatchOptions
    opts)
         Bool -> Bool -> Bool
    && Bool -> Bool
    not (Pattern -> Bool
    isLiteral (Pattern -> Bool) -> ([Token] -> Pattern) -> [Token] -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . [Token] -> Pattern
    Pattern ([Token] -> Bool) -> [Token] -> Bool
    forall a b. (a -> b) -> a -> b
    $ Int -> [Token] -> [Token]
    forall a. Int -> [a] -> [a]
    take 1 [Token]
    pat) = Bool
    False

    begMatch opts :: MatchOptions
    opts pat :: [Token]
    pat s :: FilePath
    s = MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    opts [Token]
    pat FilePath
    s

    match' :: MatchOptions -> [Token] -> FilePath -> Bool
    match' _ []                        s :: FilePath
    s  = FilePath -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null FilePath
    s
    match' _ (AnyNonPathSeparator:s :: [Token]
    s)   "" = [Token] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [Token]
    s
    match' _ _                         "" = Bool
    False
    match' o :: MatchOptions
    o (Literal l :: Char
    l       :xs :: [Token]
    xs) (c :: Char
    c:cs :: FilePath
    cs) = Char
    l Char -> Char -> Bool
    forall a. Eq a => a -> a -> Bool
    == Char
    c Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs FilePath
    cs
    match' o :: MatchOptions
    o (NonPathSeparator:xs :: [Token]
    xs) (c :: Char
    c:cs :: FilePath
    cs) =
       Bool -> Bool
    not (Char -> Bool
    isPathSeparator Char
    c) Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs FilePath
    cs

    match' o :: MatchOptions
    o (PathSeparator   :xs :: [Token]
    xs) (c :: Char
    c:cs :: FilePath
    cs) =
       Char -> Bool
    isPathSeparator Char
    c Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    begMatch MatchOptions
    o ((Token -> Bool) -> [Token] -> [Token]
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile (Token -> Token -> Bool
    forall a. Eq a => a -> a -> Bool
    == Token
    PathSeparator) [Token]
    xs)
                                       ((Char -> Bool) -> FilePath -> FilePath
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile Char -> Bool
    isPathSeparator FilePath
    cs)

    match' o :: MatchOptions
    o (CharRange b :: Bool
    b rng :: [Either Char (Char, Char)]
    rng :xs :: [Token]
    xs) (c :: Char
    c:cs :: FilePath
    cs) =
       let rangeMatch :: Either Char (Char, Char) -> Bool
    rangeMatch r :: Either Char (Char, Char)
    r =
              (Char -> Bool)
    -> ((Char, Char) -> Bool) -> Either Char (Char, Char) -> Bool
    forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
    either (Char -> Char -> Bool
    forall a. Eq a => a -> a -> Bool
    == Char
    c) ((Char, Char) -> Char -> Bool
    forall a. Ord a => (a, a) -> a -> Bool
    `inRange` Char
    c) Either Char (Char, Char)
    r Bool -> Bool -> Bool
    ||
                 -- See comment near Base.tokToLower for an explanation of why we
                 -- do this
                 MatchOptions -> Bool
    ignoreCase MatchOptions
    o Bool -> Bool -> Bool
    && (Char -> Bool)
    -> ((Char, Char) -> Bool) -> Either Char (Char, Char) -> Bool
    forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
    either (Char -> Char -> Bool
    forall a. Eq a => a -> a -> Bool
    == Char -> Char
    toUpper Char
    c) ((Char, Char) -> Char -> Bool
    forall a. Ord a => (a, a) -> a -> Bool
    `inRange` Char -> Char
    toUpper Char
    c) Either Char (Char, Char)
    r
        in Bool -> Bool
    not (Char -> Bool
    isPathSeparator Char
    c) Bool -> Bool -> Bool
    &&
           (Either Char (Char, Char) -> Bool)
    -> [Either Char (Char, Char)] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    any Either Char (Char, Char) -> Bool
    rangeMatch [Either Char (Char, Char)]
    rng Bool -> Bool -> Bool
    forall a. Eq a => a -> a -> Bool
    == Bool
    b Bool -> Bool -> Bool
    &&
           MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs FilePath
    cs

    match' o :: MatchOptions
    o (OpenRange lo :: Maybe FilePath
    lo hi :: Maybe FilePath
    hi :xs :: [Token]
    xs) path :: FilePath
    path =
       let getNumChoices :: [a] -> [([a], [a])]
    getNumChoices n :: [a]
    n =
              [([a], [a])] -> [([a], [a])]
    forall a. [a] -> [a]
    tail ([([a], [a])] -> [([a], [a])])
    -> ([Int] -> [([a], [a])]) -> [Int] -> [([a], [a])]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (([a], [a]) -> Bool) -> [([a], [a])] -> [([a], [a])]
    forall a. (a -> Bool) -> [a] -> [a]
    takeWhile (Bool -> Bool
    not(Bool -> Bool) -> (([a], [a]) -> Bool) -> ([a], [a]) -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    .[a] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null([a] -> Bool) -> (([a], [a]) -> [a]) -> ([a], [a]) -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    .([a], [a]) -> [a]
    forall a b. (a, b) -> b
    snd) ([([a], [a])] -> [([a], [a])])
    -> ([Int] -> [([a], [a])]) -> [Int] -> [([a], [a])]
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (Int -> ([a], [a])) -> [Int] -> [([a], [a])]
    forall a b. (a -> b) -> [a] -> [b]
    map (Int -> [a] -> ([a], [a])
    forall a. Int -> [a] -> ([a], [a])
    `splitAt` [a]
    n) ([Int] -> [([a], [a])]) -> [Int] -> [([a], [a])]
    forall a b. (a -> b) -> a -> b
    $ [0..]
           (lzNum :: FilePath
    lzNum,cs :: FilePath
    cs) = (Char -> Bool) -> FilePath -> (FilePath, FilePath)
    forall a. (a -> Bool) -> [a] -> ([a], [a])
    span Char -> Bool
    isDigit FilePath
    path
           num :: FilePath
    num        = FilePath -> FilePath
    dropLeadingZeroes FilePath
    lzNum
           numChoices :: [(FilePath, FilePath)]
    numChoices = FilePath -> [(FilePath, FilePath)]
    forall a. [a] -> [([a], [a])]
    getNumChoices FilePath
    num
           zeroChoices :: [(FilePath, FilePath)]
    zeroChoices = ((FilePath, FilePath) -> Bool)
    -> [(FilePath, FilePath)] -> [(FilePath, FilePath)]
    forall a. (a -> Bool) -> [a] -> [a]
    takeWhile ((Char -> Bool) -> FilePath -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all (Char -> Char -> Bool
    forall a. Eq a => a -> a -> Bool
    =='0') (FilePath -> Bool)
    -> ((FilePath, FilePath) -> FilePath)
    -> (FilePath, FilePath)
    -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    . (FilePath, FilePath) -> FilePath
    forall a b. (a, b) -> a
    fst) (FilePath -> [(FilePath, FilePath)]
    forall a. [a] -> [([a], [a])]
    getNumChoices FilePath
    lzNum)
        in -- null lzNum means no digits: definitely not a match
           Bool -> Bool
    not (FilePath -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null FilePath
    lzNum) Bool -> Bool -> Bool
    &&
              -- So, given the path "00123foo" what we've got is:
              --    lzNum       = "00123"
              --    cs          = "foo"
              --    num         = "123"
              --    numChoices  = [("1","23"),("12","3")]
              --    zeroChoices = [("0", "0123"), ("00", "123")]
              --
              -- We want to try matching x against each of 123, 12, and 1.
              -- 12 and 1 are in numChoices already, but we need to add (num,"")
              -- manually.
              --
              -- It's also possible that we only want to match the zeroes. Handle
              -- that separately since inOpenRange doesn't like leading zeroes.
              (((FilePath, FilePath) -> Bool) -> [(FilePath, FilePath)] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    any (\(n :: FilePath
    n,rest :: FilePath
    rest) -> Maybe FilePath -> Maybe FilePath -> FilePath -> Bool
    inOpenRange Maybe FilePath
    lo Maybe FilePath
    hi FilePath
    n Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs (FilePath
    rest FilePath -> FilePath -> FilePath
    forall a. [a] -> [a] -> [a]
    ++ FilePath
    cs))
                   ((FilePath
    num,"") (FilePath, FilePath)
    -> [(FilePath, FilePath)] -> [(FilePath, FilePath)]
    forall a. a -> [a] -> [a]
    : [(FilePath, FilePath)]
    numChoices)
               Bool -> Bool -> Bool
    || (Bool -> Bool
    not ([(FilePath, FilePath)] -> Bool
    forall (t :: * -> *) a. Foldable t => t a -> Bool
    null [(FilePath, FilePath)]
    zeroChoices) Bool -> Bool -> Bool
    && Maybe FilePath -> Maybe FilePath -> FilePath -> Bool
    inOpenRange Maybe FilePath
    lo Maybe FilePath
    hi "0"
                   Bool -> Bool -> Bool
    && ((FilePath, FilePath) -> Bool) -> [(FilePath, FilePath)] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    any (\(_,rest :: FilePath
    rest) -> MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs (FilePath
    rest FilePath -> FilePath -> FilePath
    forall a. [a] -> [a] -> [a]
    ++ FilePath
    cs)) [(FilePath, FilePath)]
    zeroChoices))

    match' o :: MatchOptions
    o again :: [Token]
    again@(AnyNonPathSeparator:xs :: [Token]
    xs) path :: FilePath
    path@(c :: Char
    c:cs :: FilePath
    cs) =
       MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs FilePath
    path Bool -> Bool -> Bool
    || (Bool -> Bool
    not (Char -> Bool
    isPathSeparator Char
    c) Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    again FilePath
    cs)

    match' o :: MatchOptions
    o (AnyDirectory:xs :: [Token]
    xs) path :: FilePath
    path =
       if MatchOptions -> Bool
    matchDotsImplicitly MatchOptions
    o
          then Bool
    hasMatch
          --  **/baz shouldn't match foo/.bar/baz, so check that none of the
          -- directories matched by **/ start with .
          else Bool
    hasMatch Bool -> Bool -> Bool
    && (FilePath -> Bool) -> [FilePath] -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all (Bool -> Bool
    not(Bool -> Bool) -> (FilePath -> Bool) -> FilePath -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    .Char -> Bool
    isExtSeparator(Char -> Bool) -> (FilePath -> Char) -> FilePath -> Bool
    forall b c a. (b -> c) -> (a -> b) -> a -> c
    .FilePath -> Char
    forall a. [a] -> a
    head) [FilePath]
    matchedDirs
     where parts :: [FilePath]
    parts   = FilePath -> [FilePath]
    pathParts ((Char -> Bool) -> FilePath -> FilePath
    forall a. (a -> Bool) -> [a] -> [a]
    dropWhile Char -> Bool
    isPathSeparator FilePath
    path)
           matchIndex :: Maybe Int
    matchIndex = (FilePath -> Bool) -> [FilePath] -> Maybe Int
    forall a. (a -> Bool) -> [a] -> Maybe Int
    findIndex (MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs) [FilePath]
    parts
           hasMatch :: Bool
    hasMatch = Maybe Int -> Bool
    forall a. Maybe a -> Bool
    isJust Maybe Int
    matchIndex
           matchedDirs :: [FilePath]
    matchedDirs = Int -> [FilePath] -> [FilePath]
    forall a. Int -> [a] -> [a]
    take (Int -> Maybe Int -> Int
    forall a. a -> Maybe a -> a
    fromMaybe 0 Maybe Int
    matchIndex) [FilePath]
    parts

    match' o :: MatchOptions
    o (LongLiteral len :: Int
    len s :: FilePath
    s:xs :: [Token]
    xs) path :: FilePath
    path =
       let (pre :: FilePath
    pre,cs :: FilePath
    cs) = Int -> FilePath -> (FilePath, FilePath)
    forall a. Int -> [a] -> ([a], [a])
    splitAt Int
    len FilePath
    path
        in FilePath
    pre FilePath -> FilePath -> Bool
    forall a. Eq a => a -> a -> Bool
    == FilePath
    s Bool -> Bool -> Bool
    && MatchOptions -> [Token] -> FilePath -> Bool
    match' MatchOptions
    o [Token]
    xs FilePath
    cs

    match' _ (Unmatchable:_) _ = Bool
    False
    match' _ (ExtSeparator:_) _ = FilePath -> Bool
    forall a. HasCallStack => FilePath -> a
    error "ExtSeparator survived optimization?"

    -- Does the actual open range matching: finds whether the third parameter
    -- is between the first two or not.
    --
    -- It does this by keeping track of the Ordering so far (e.g. having
    -- looked at "12" and "34" the Ordering of the two would be LT: 12 < 34)
    -- and aborting if a String "runs out": a longer string is automatically
    -- greater.
    --
    -- Assumes that the input strings contain only digits, and no leading zeroes.
    inOpenRange :: Maybe String -> Maybe String -> String -> Bool
    inOpenRange :: Maybe FilePath -> Maybe FilePath -> FilePath -> Bool
    inOpenRange l_ :: Maybe FilePath
    l_ h_ :: Maybe FilePath
    h_ s_ :: FilePath
    s_ = Bool -> Bool -> Bool
    forall a. HasCallStack => Bool -> a -> a
    assert ((Char -> Bool) -> FilePath -> Bool
    forall (t :: * -> *) a. Foldable t => (a -> Bool) -> t a -> Bool
    all Char -> Bool
    isDigit FilePath
    s_) (Bool -> Bool) -> Bool -> Bool
    forall a b. (a -> b) -> a -> b
    $ Maybe FilePath
    -> Maybe FilePath -> FilePath -> Ordering -> Ordering -> Bool
    forall a.
    Ord a =>
    Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go Maybe FilePath
    l_ Maybe FilePath
    h_ FilePath
    s_ Ordering
    EQ Ordering
    EQ
     where
       go :: Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go Nothing      Nothing   _     _ _  = Bool
    True  -- no bounds
       go (Just [])    _         []    LT _ = Bool
    False --  lesser than lower bound
       go _            (Just []) _     _ GT = Bool
    False -- greater than upper bound
       go _            (Just []) (_:_) _ _  = Bool
    False --  longer than upper bound
       go (Just (_:_)) _         []    _ _  = Bool
    False -- shorter than lower bound
       go _            _         []    _ _  = Bool
    True

       go (Just (l :: a
    l:ls :: [a]
    ls)) (Just (h :: a
    h:hs :: [a]
    hs)) (c :: a
    c:cs :: [a]
    cs) ordl :: Ordering
    ordl ordh :: Ordering
    ordh =
          let ordl' :: Ordering
    ordl' = Ordering
    ordl Ordering -> Ordering -> Ordering
    forall a. Monoid a => a -> a -> a
    `mappend` a -> a -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare a
    c a
    l
              ordh' :: Ordering
    ordh' = Ordering
    ordh Ordering -> Ordering -> Ordering
    forall a. Monoid a => a -> a -> a
    `mappend` a -> a -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare a
    c a
    h
           in Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go ([a] -> Maybe [a]
    forall a. a -> Maybe a
    Just [a]
    ls) ([a] -> Maybe [a]
    forall a. a -> Maybe a
    Just [a]
    hs) [a]
    cs Ordering
    ordl' Ordering
    ordh'

       go Nothing (Just (h :: a
    h:hs :: [a]
    hs)) (c :: a
    c:cs :: [a]
    cs) _ ordh :: Ordering
    ordh =
          let ordh' :: Ordering
    ordh' = Ordering
    ordh Ordering -> Ordering -> Ordering
    forall a. Monoid a => a -> a -> a
    `mappend` a -> a -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare a
    c a
    h
           in Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go Maybe [a]
    forall a. Maybe a
    Nothing ([a] -> Maybe [a]
    forall a. a -> Maybe a
    Just [a]
    hs) [a]
    cs Ordering
    GT Ordering
    ordh'

       go (Just (l :: a
    l:ls :: [a]
    ls)) Nothing (c :: a
    c:cs :: [a]
    cs) ordl :: Ordering
    ordl _ =
          let ordl' :: Ordering
    ordl' = Ordering
    ordl Ordering -> Ordering -> Ordering
    forall a. Monoid a => a -> a -> a
    `mappend` a -> a -> Ordering
    forall a. Ord a => a -> a -> Ordering
    compare a
    c a
    l
           in Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go ([a] -> Maybe [a]
    forall a. a -> Maybe a
    Just [a]
    ls) Maybe [a]
    forall a. Maybe a
    Nothing [a]
    cs Ordering
    ordl' Ordering
    LT

       -- lower bound is shorter: s is greater
       go (Just []) hi :: Maybe [a]
    hi s :: [a]
    s _ ordh :: Ordering
    ordh = Maybe [a] -> Maybe [a] -> [a] -> Ordering -> Ordering -> Bool
    go Maybe [a]
    forall a. Maybe a
    Nothing Maybe [a]
    hi [a]
    s Ordering
    GT Ordering
    ordh