Add some asserts and comments

Author: harendra-kumar

core/src/Streamly/Internal/Data/Array.hs

@@ -932,6 +932,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SPartial 1 s ->
                  goArray s [] st (Array contents next end)
             Parser.SPartial m s -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length (x:backBuf)) (return ())
                 let src0 = Prelude.take n (x:backBuf)
@@ -942,6 +943,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SContinue 1 s ->
                 goArray s (x:backBuf) st (Array contents next end)
             Parser.SContinue m s -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length (x:backBuf)) (return ())
                 let (src0, buf1) = Prelude.splitAt n (x:backBuf)
@@ -953,6 +955,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
                 let arr = Array contents next end
                 return (Right b, StreamK.cons arr st)
             Parser.SDone m b -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length (x:backBuf)) (return ())
                 let src0 = Prelude.take n (x:backBuf)
@@ -980,6 +983,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SPartial 1 s ->
                  goExtract s [] (Array contents next end)
             Parser.SPartial m s -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length (x:backBuf)) (return ())
                 let src0 = Prelude.take n (x:backBuf)
@@ -990,6 +994,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SContinue 1 s ->
                 goExtract s backBuf (Array contents next end)
             Parser.SContinue m s -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length (x:backBuf)) (return ())
                 let (src0, buf1) = Prelude.splitAt n (x:backBuf)
@@ -1001,6 +1006,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
                 let arr = Array contents next end
                 return (Right b, StreamK.fromPure arr)
             Parser.SDone m b -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length backBuf) (return ())
                 let src0 = Prelude.take n (x:backBuf)
@@ -1026,6 +1032,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SContinue 1 s ->
                 goStop s backBuf
             Parser.SContinue m s -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length backBuf) (return ())
                 let (src0, buf1) = Prelude.splitAt n backBuf
@@ -1034,6 +1041,7 @@ parseBreakChunksK (Parser pstep initial extract) stream = do
             Parser.SDone 1 b ->
                 return (Right b, StreamK.nil)
             Parser.SDone m b -> do
+                assertM(m <= 1)
                 let n = 1 - m
                 assert (n <= Prelude.length backBuf) (return ())
                 let src0 = Prelude.take n backBuf

core/src/Streamly/Internal/Data/Parser/Type.hs

@@ -293,6 +293,11 @@ instance Functor (Initial s) where
 --
 -- Folds can only return the right values. Parsers can also return lefts.
 
+-- XXX If we assume that the current position of the stream includes the
+-- element being processed then we can use 'SPartial 0' in the common cases, no
+-- change from current, and the change required would be just inverting the
+-- sign of the arguments.
+
 -- | The return type of a 'Parser' step.
 --
 -- The parser driver feeds the input stream to the parser one element at a