Change the notion on ParserK.Step

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

@@ -1048,28 +1048,31 @@ parseBreak parser input = do
             -- If we stop in an alternative, it will try calling the next
             -- parser, the next parser may call initial returning Partial and
             -- then immediately we have to call extract on it.
-            ParserK.Partial 0 cont1 ->
+            ParserK.SPartial (-1) cont1 ->
                  go [] cont1 StreamK.nil
-            ParserK.Partial n cont1 -> do
-                let n1 = negate n
+            ParserK.SPartial m cont1 -> do
+                let n = m + 1
+                    n1 = negate n
                 assertM(n1 >= 0 && n1 <= sum (Prelude.map length backBuf))
                 let (s1, backBuf1) = backTrack n1 backBuf StreamK.nil
                  in go backBuf1 cont1 s1
-            ParserK.Continue 0 cont1 ->
+            ParserK.SContinue (-1) cont1 ->
                 go backBuf cont1 StreamK.nil
-            ParserK.Continue n cont1 -> do
-                let n1 = negate n
+            ParserK.SContinue m cont1 -> do
+                let n = m + 1
+                    n1 = negate n
                 assertM(n1 >= 0 && n1 <= sum (Prelude.map length backBuf))
                 let (s1, backBuf1) = backTrack n1 backBuf StreamK.nil
                  in go backBuf1 cont1 s1
-            ParserK.Done 0 b ->
+            ParserK.SDone (-1) b ->
                 return (Right b, StreamK.nil)
-            ParserK.Done n b -> do
-                let n1 = negate n
+            ParserK.SDone m b -> do
+                let n = m + 1
+                    n1 = negate n
                 assertM(n1 >= 0 && n1 <= sum (Prelude.map length backBuf))
                 let (s1, _) = backTrack n1 backBuf StreamK.nil
                  in return (Right b, s1)
-            ParserK.Error _ err -> do
+            ParserK.SError _ err -> do
                 let (s1, _) = backTrack maxBound backBuf StreamK.nil
                 return (Left (ParseError err), s1)
 
@@ -1081,7 +1084,8 @@ parseBreak parser input = do
         pRes <- parserk (ParserK.Chunk arr)
         let len = length arr
         case pRes of
-            ParserK.Partial n cont1 ->
+            ParserK.SPartial m cont1 -> do
+                let n = m + 1
                 case compare n len of
                     EQ -> go [] cont1 stream
                     LT -> do
@@ -1095,7 +1099,8 @@ parseBreak parser input = do
                             let (s1, _) = backTrack n1 backBuf s
                             go [] cont1 s1
                     GT -> seekErr n len
-            ParserK.Continue n cont1 ->
+            ParserK.SContinue m cont1 -> do
+                let n = m + 1
                 case compare n len of
                     EQ -> go (arr:backBuf) cont1 stream
                     LT -> do
@@ -1109,12 +1114,13 @@ parseBreak parser input = do
                             let (s1, backBuf1) = backTrack n1 backBuf s
                             go backBuf1 cont1 s1
                     GT -> seekErr n len
-            ParserK.Done n b -> do
-                let n1 = len - n
+            ParserK.SDone m b -> do
+                let n = m + 1
+                    n1 = len - n
                 assertM(n1 <= sum (Prelude.map length (arr:backBuf)))
                 let (s1, _) = backTrack n1 (arr:backBuf) stream
                  in return (Right b, s1)
-            ParserK.Error _ err -> do
+            ParserK.SError _ err -> do
                 let (s1, _) = backTrack maxBound (arr:backBuf) stream
                 return (Left (ParseError err), s1)
 

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

@@ -1,3 +1,5 @@
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE ViewPatterns #-}
 -- |
 -- Module      : Streamly.Internal.Data.Parser.ParserK.Type
 -- Copyright   : (c) 2020 Composewell Technologies
@@ -23,7 +25,7 @@
 
 module Streamly.Internal.Data.ParserK.Type
     (
-      Step (..)
+      Step(Partial, Continue, Done, Error, SPartial, SContinue, SDone, SError)
     , Input (..)
     , ParseResult (..)
     , ParserK (..)
@@ -121,12 +123,40 @@ type StepParser a m r = Input a -> m (Step a m r)
 -- /Pre-release/
 --
 data Step a m r =
-    -- The Int is the current stream position index wrt to the start of the
-    -- array.
-      Done !Int r
-    | Partial !Int (StepParser a m r)
-    | Continue !Int (StepParser a m r)
-    | Error !Int String
+      SDone !Int r
+    | SPartial !Int (StepParser a m r)
+    | SContinue !Int (StepParser a m r)
+    | SError !Int String
+
+--------------------------------------------------------------------------------
+-- Custom Patterns
+--------------------------------------------------------------------------------
+
+incrIndex :: Step a m r -> Step a m r
+incrIndex (SPartial i s) = SPartial (i + 1) s
+incrIndex (SContinue i s) = SContinue (i + 1) s
+incrIndex (SDone i b) = SDone (i + 1) b
+incrIndex (SError i s) = SError (i + 1) s
+
+pattern Partial :: Int -> StepParser a m r -> Step a m r
+pattern Partial i s <- (incrIndex -> SPartial i s)
+    where Partial i s = SPartial (i - 1) s
+
+pattern Continue :: Int -> StepParser a m r -> Step a m r
+pattern Continue i s <- (incrIndex -> SContinue i s)
+    where Continue i s = SContinue (i - 1) s
+
+pattern Done :: Int -> r -> Step a m r
+pattern Done i b <- (incrIndex -> SDone i b)
+    where Done i b = SDone (i - 1) b
+
+pattern Error :: Int -> String -> Step a m r
+pattern Error i b <- (incrIndex -> SError i b)
+    where Error i b = SError (i - 1) b
+
+--------------------------------------------------------------------------------
+-- Code
+--------------------------------------------------------------------------------
 
 instance Functor m => Functor (Step a m) where
     fmap f (Done n r) = Done n (f r)