regex interpreter now can build partial correct AST (i forget groups), but in bad shape. building an optimizer.

StgSharp.RegularAnalysis/Abstraction/AbstractSyntaxTree.cs

@@ -29,6 +29,7 @@ using StgSharp.Collections;
 
 using System;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using System.Text;
 using System.Xml.Schema;
 
@@ -38,6 +39,8 @@ namespace StgSharp.RegularAnalysis.Abstraction
         where TType : unmanaged
     {
 
+        private HashSet<TNode> _allToken = new();
+
         private TNode _root;
 
         public int Count
@@ -45,17 +48,31 @@ namespace StgSharp.RegularAnalysis.Abstraction
             get { return _allToken.Count; }
         }
 
-        public TNode Root => _root;
+        public TNode Root
+        {
+            get;
+            internal set
+            {
+                if (_allToken.Contains(value)) {
+                    field = value;
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool AddNode(
+                    TNode node
+        )
+        {
+            return _allToken.Add(node);
+        }
 
         public bool Contains(
                     TNode node
         )
         {
-            return _allToken<TLabel>.Contains(node);
+            return _allToken.Contains(node);
         }
 
-        private List<TNode> _allToken<TLabel> = 
-new();
-
     }
 }

StgSharp.RegularAnalysis/Abstraction/CompileStack.cs

@@ -47,7 +47,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
 
         public CompileStack()
         {
-            _depthMarks.Push(new DepthMark(0, 0));
+            _depthMarks.Push(new DepthMark(0, 0, 0));
         }
 
         public int OperandInDepthCount
@@ -59,7 +59,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
         public int OperatorInDepthCount
         {
             [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            get => _operands.Count - _depthMarks.Peek().OperandPos;
+            get => _operators.Count - _depthMarks.Peek().OperandPos;
         }
 
         public int Depth
@@ -108,6 +108,20 @@ namespace StgSharp.RegularAnalysis.Abstraction
             return false;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool TryPeekOperator(
+                    out TNode op
+        )
+        {
+            if (OperatorInDepthCount > 0)
+            {
+                op = _operators.Peek();
+                return true;
+            }
+            op = TNode.Empty;
+            return false;
+        }
+
             #endregion
 
         #region operand
@@ -117,7 +131,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
         )
         {
             if (OperatorInDepthCount > 0) {
-                return _operators.Pop();
+                return _operands.Pop();
             }
             return TNode.Empty;
         }
@@ -127,7 +141,7 @@ namespace StgSharp.RegularAnalysis.Abstraction
                     TNode operatorNode
         )
         {
-            _operators.Push(operatorNode);
+            _operands.Push(operatorNode);
         }
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -144,6 +158,20 @@ namespace StgSharp.RegularAnalysis.Abstraction
             return false;
         }
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool TryPeekOperand(
+                    out TNode op
+        )
+        {
+            if (OperandInDepthCount > 0)
+            {
+                op = _operands.Peek();
+                return true;
+            }
+            op = TNode.Empty;
+            return false;
+        }
+
             #endregion
 
         #region depth

StgSharp.RegularAnalysis/Abstraction/Token.cs

@@ -45,6 +45,14 @@ namespace StgSharp.RegularAnalysis.Abstraction
         public readonly string Value;
         public readonly TLabel Flag;
 
+        public Token()
+        {
+            Column = 0;
+            Line = 0;
+            Value = string.Empty;
+            Flag = default;
+        }
+
         public Token(
                string chars,
                int lineNumber,