Fix take, takeEQ, takeGE, sliceSepByMax.

- `take`, `takeEQ`, `takeGE` now work when the count is <0.
- `sliceSepByMax` behaviour is now more in line with what the
  documentaton says in `Streamly.Internal.Data.Parser`.

src/Streamly/Internal/Data/Parser.hs

@@ -381,6 +381,9 @@ satisfy = D.toParserK . D.satisfy
 -- >>> S.parse (PR.take 1 FL.toList) $ S.fromList [1]
 -- [1]
 --
+-- >>> S.parse (PR.take (-1) FL.toList) $ S.fromList [1]
+-- []
+--
 -- @
 -- S.chunksOf n f = S.splitParse (FL.take n f)
 -- @
@@ -515,6 +518,13 @@ sliceBeginWith = undefined
 -- hybrid of 'splitOn' and 'take'. The element on which the condition succeeds
 -- is dropped.
 --
+-- >>> even n = n `mod` 2 == 0
+-- >>> S.parse (PR.many FL.toList (PR.sliceSepByMax (==1) 5 FL.toList)) $ S.fromList [1..10]
+-- > [[],[2,3,4,5,6],[7,8,9,10]]
+--
+-- >>> S.parse (PR.many FL.toList (PR.sliceSepByMax even 10 FL.toList)) $ S.fromList [0..10]
+-- > [[],[1],[3],[5],[7],[9],[]]
+--
 -- /Internal/
 --
 {-# INLINABLE sliceSepByMax #-}

src/Streamly/Internal/Data/Parser/ParserD.hs

@@ -316,13 +316,15 @@ take n (Fold fstep finitial fextract) = Parser step initial extract
 
     initial = Tuple' 0 <$> finitial
 
-    step (Tuple' i r) a = do
-        res <- fstep r a
-        let i1 = i + 1
-            s1 = Tuple' i1 res
-        if i1 < n
-        then return $ Partial 0 s1
-        else Done 0 <$> fextract res
+    step (Tuple' i r) a
+        | i < n = do
+            res <- fstep r a
+            let i1 = i + 1
+                s1 = Tuple' i1 res
+            if i1 < n
+            then return $ Partial 0 s1
+            else Done 0 <$> fextract res
+        | otherwise = Done 1 <$> fextract r
 
     extract (Tuple' _ r) = fextract r
 
@@ -338,11 +340,15 @@ takeEQ n (Fold fstep finitial fextract) = Parser step initial extract
 
     initial = Tuple' 0 <$> finitial
 
-    step (Tuple' i r) a = do
-        res <- fstep r a
-        let i1 = i + 1
-            s1 = Tuple' i1 res
-        if i1 < n then return (Continue 0 s1) else Done 0 <$> fextract res
+    step (Tuple' i r) a
+      | i < n = do
+          res <- fstep r a
+          let i1 = i + 1
+              s1 = Tuple' i1 res
+          if i1 < n
+          then return (Continue 0 s1)
+          else Done 0 <$> fextract res
+      | otherwise = Done 1 <$> fextract r
 
     extract (Tuple' i r) =
         if n == i
@@ -361,10 +367,11 @@ takeEQ n (Fold fstep finitial fextract) = Parser step initial extract
 --
 {-# INLINE takeGE #-}
 takeGE :: MonadThrow m => Int -> Fold m a b -> Parser m a b
-takeGE n (Fold fstep finitial fextract) = Parser step initial extract
-
+takeGE cnt (Fold fstep finitial fextract) = Parser step initial extract
     where
 
+    n = max cnt 0
+
     initial = Tuple' 0 <$> finitial
 
     step (Tuple' i r) a = do
@@ -489,17 +496,18 @@ sliceSepByMax predicate cnt (Fold fstep finitial fextract) =
     where
 
     initial = Tuple' 0 <$> finitial
+
     step (Tuple' i r) a
-        | not (predicate a) = do
-            res <- fstep r a
-            let i1 = i + 1
-                s1 = Tuple' i1 res
-            if i1 < cnt
-            then return $ Partial 0 s1
-            else do
-                b <- fextract res
-                return $ Done 0 b
+        | not (predicate a) =
+            if i < cnt
+            then do
+                res <- fstep r a
+                let i1 = i + 1
+                    s1 = Tuple' i1 res
+                return $ Partial 0 s1
+            else Done 1 <$> fextract r
         | otherwise = Done 0 <$> fextract r
+
     extract (Tuple' _ r) = fextract r
 
 -- | See 'Streamly.Internal.Data.Parser.wordBy'.