--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Implab/Automaton/RegularExpressions/Token.cs	Fri Apr 22 13:08:08 2016 +0300
@@ -0,0 +1,63 @@
+using Implab;
+using System;
+using System.Linq;
+
+namespace Implab.Automaton.RegularExpressions {
+    public abstract class Token {
+        public abstract void Accept(IVisitor visitor);
+
+        public Token End() {
+            return Cat(new EndToken());
+        }
+
+        public Token Tag<TTag>(TTag tag) {
+            return Cat(new EndToken<TTag>(tag));
+        }
+
+        public Token Cat(Token right) {
+            return new CatToken(this, right);
+        }
+
+        public Token Or(Token right) {
+            return new AltToken(this, right);
+        }
+
+        public Token Optional() {
+            return Or(new EmptyToken());
+        }
+
+        public Token EClosure() {
+            return new StarToken(this);
+        }
+
+        public Token Closure() {
+            return Cat(new StarToken(this));
+        }
+
+        public Token Repeat(int count) {
+            Token token = null;
+
+            for (int i = 0; i < count; i++)
+                token = token != null ? token.Cat(this) : this;
+            return token ?? new EmptyToken();
+        }
+
+        public Token Repeat(int min, int max) {
+            if (min > max || min < 1)
+                throw new ArgumentOutOfRangeException();
+            var token = Repeat(min);
+
+            for (int i = min; i < max; i++)
+                token = token.Cat( Optional() );
+            return token;
+        }
+
+        public static Token New(params int[] set) {
+            Safe.ArgumentNotNull(set, "set");
+            Token token = null;
+            foreach(var c in set.Distinct())
+                token = token == null ? new SymbolToken(c) : token.Or(new SymbolToken(c));
+            return token;
+        }
+    }
+}