Indirect left recursion should now work properly

2 files changed, 62 insertions, 24 deletions

diff --git a/src/packrat-parsers.adb b/src/packrat-parsers.adb
index 06a0b00..01c4677 100644
--- a/src/packrat-parsers.adb
+++ b/src/packrat-parsers.adb
@@ -120,18 +120,29 @@ package body Packrat.Parsers is
 
     function Reusable
            (Result   : in Combinator_Result;
-            Position : in Positive;
+            Main_Key : in Combo_Key;
             Leftrecs : in Leftrectables.Map)
         return Boolean
     is
+        Position : Positive := Main_Key.Start;
         Working_Key : Combo_Key;
     begin
         for Cursor in Result.Curtails.Iterate loop
             Working_Key := To_Key (Position, Curtail_Maps.Key (Cursor));
-            if Leftrecs.Contains (Working_Key) and then
-                Curtail_Maps.Element (Cursor) > Leftrecs.Element (Working_Key)
-            then
-                return False;
+            if Working_Key = Main_Key then
+                if not Leftrecs.Contains (Working_Key) then
+                    if Curtail_Maps.Element (Cursor) > 1 then
+                        return False;
+                    end if;
+                elsif Curtail_Maps.Element (Cursor) > Leftrecs.Element (Working_Key) + 1 then
+                    return False;
+                end if;
+            else
+                if not Leftrecs.Contains (Working_Key) or else
+                    Curtail_Maps.Element (Cursor) > Leftrecs.Element (Working_Key)
+                then
+                    return False;
+                end if;
             end if;
         end loop;
         return True;
@@ -142,12 +153,14 @@ package body Packrat.Parsers is
            (Context : in out Parser_Context)
         return Combinator_Result
     is
-        Result : Combinator_Result;
+        Result, Previous : Combinator_Result;
+        Combo : Combinator;
+        Left : Positive;
     begin
         if Context.Memotable.Contains (My_Key) then
-            Result := Context.Memotable.Element (My_Key);
-            if Reusable (Result, My_Key.Start, Context.Leftrectable) then
-                return Result;
+            Previous := Context.Memotable.Element (My_Key);
+            if Reusable (Previous, My_Key, Context.Leftrectable) then
+                return Previous;
             end if;
         end if;
         if My_Key.Start < Context.Current_Position then
@@ -158,6 +171,28 @@ package body Packrat.Parsers is
             Context.Needs_More.Include (My_Key.Start);
         end if;
         if Context.Memotable.Contains (My_Key) then
+            for C in Previous.Curtails.Iterate loop
+                Combo := Curtail_Maps.Key (C);
+                if Context.Leftrectable.Contains (To_Key (My_Key.Start, Combo)) then
+                    Left := Context.Leftrectable.Element (To_Key (My_Key.Start, Combo));
+                    if Combo = My_Key.Func then
+                        Left := Left + 1;
+                    end if;
+                    if Result.Curtails.Contains (Combo) then
+                        Result.Curtails.Replace (Combo, Left);
+                    else
+                        Result.Curtails.Insert (Combo, Left);
+                    end if;
+                else
+                    if Combo = My_Key.Func then
+                        if Result.Curtails.Contains (Combo) then
+                            Result.Curtails.Replace (Combo, 1);
+                        else
+                            Result.Curtails.Insert (Combo, 1);
+                        end if;
+                    end if;
+                end if;
+            end loop;
             Context.Memotable.Replace (My_Key, Result);
         else
             Context.Memotable.Insert (My_Key, Result);
@@ -237,9 +272,7 @@ package body Packrat.Parsers is
     begin
         for Curse in Add.Iterate loop
             if Target.Contains (Curtail_Maps.Key (Curse)) then
-                if Target.Element (Curtail_Maps.Key (Curse)) >
-                    Add.Element (Curtail_Maps.Key (Curse))
-                then
+                if Target.Element (Curtail_Maps.Key (Curse)) > Curtail_Maps.Element (Curse) then
                     Target.Replace (Curtail_Maps.Key (Curse), Curtail_Maps.Element (Curse));
                 end if;
             else
@@ -263,6 +296,7 @@ package body Packrat.Parsers is
            (Target : in out Combinator_Result;
             Add    : in     Combinator_Result) is
     begin
+        Merge (Target.Curtails, Add.Curtails);
         case Target.Status is
             when Success =>
                 case Add.Status is
@@ -286,17 +320,22 @@ package body Packrat.Parsers is
             when Needs_More =>
                 case Add.Status is
                     when Success | Optional_More =>
-                        Target := Add;
+                        Target.Results.Union (Add.Results);
                         Target.Status := Optional_More;
                     when Needs_More | Failure =>
                         null;
                 end case;
             when Failure =>
-                if Add.Status = Failure then
-                    Merge (Target.Curtails, Add.Curtails);
-                else
-                    Target := Add;
-                end if;
+                case Add.Status is
+                    when Success | Optional_More =>
+                        Target.Results.Union (Add.Results);
+                        Target.Status := Add.Status;
+                    when Needs_More =>
+                        null;
+                        Target.Status := Add.Status;
+                    when Failure =>
+                        null;
+                end case;
         end case;
     end Merge;
 
@@ -589,7 +628,8 @@ package body Packrat.Parsers is
             Salt.Results := Processed;
             return Salt;
         end Actual;
-        function Memo is new Memoize (To_Key (Start, Stamp'Access), Actual);
+        function Curt is new Curtailment (To_Key (Start, Stamp'Access), Input, Actual);
+        function Memo is new Memoize (To_Key (Start, Stamp'Access), Curt);
     begin
         return Memo (Context);
     end Stamp;
@@ -617,7 +657,8 @@ package body Packrat.Parsers is
             Salt.Results := Processed;
             return Salt;
         end Actual;
-        function Memo is new Memoize (To_Key (Start, Ignore'Access), Actual);
+        function Curt is new Curtailment (To_Key (Start, Ignore'Access), Input, Actual);
+        function Memo is new Memoize (To_Key (Start, Ignore'Access), Curt);
     begin
         return Memo (Context);
     end Ignore;
@@ -727,9 +768,6 @@ package body Packrat.Parsers is
         is
             Salt : Combinator_Result;
         begin
-            if Params'Length = 0 then
-                return Empty (Input, Context, Start);
-            end if;
             for C of Params loop
                 Merge (Salt, C (Input, Context, Start));
             end loop;
diff --git a/src/packrat-parsers.ads b/src/packrat-parsers.ads
index e11d623..6040f4f 100644
--- a/src/packrat-parsers.ads
+++ b/src/packrat-parsers.ads
@@ -599,7 +599,7 @@ private
 
     function Reusable
            (Result   : in Combinator_Result;
-            Position : in Positive;
+            Main_Key : in Combo_Key;
             Leftrecs : in Leftrectables.Map)
         return Boolean;