diff --git a/example/math_expression/main.go b/example/math_expression/main.go
index bfece39..805028e 100644
--- a/example/math_expression/main.go
+++ b/example/math_expression/main.go
@@ -1,5 +1,3 @@
-// +build example
-
 package main
 
 import (
@@ -8,6 +6,13 @@ import (
 	"github.com/neonxp/unilex"
 )
 
+const (
+	LP unilex.LexType = iota
+	RP
+	NUMBER
+	OPERATOR
+)
+
 func main() {
 
 	l := unilex.New("10 * (20.0 + 30.0)")
@@ -29,13 +34,13 @@ func lexExpression(l *unilex.Lexer) unilex.StateFunc {
 
 	switch {
 	case l.Accept("("):
-		l.Emit("LP")
+		l.Emit(LP)
 	case l.Accept(")"):
-		l.Emit("RP")
+		l.Emit(RP)
 	case unilex.ScanNumber(l):
-		l.Emit("NUMBER")
+		l.Emit(NUMBER)
 	case l.Accept("+-*/^!"):
-		l.Emit("OPERATOR")
+		l.Emit(OPERATOR)
 	case l.Peek() == unilex.EOF:
 		return nil
 	default:
diff --git a/example/math_expression/rpn.go b/example/math_expression/rpn.go
index 84de59c..a4cacc0 100644
--- a/example/math_expression/rpn.go
+++ b/example/math_expression/rpn.go
@@ -1,5 +1,3 @@
-// +build example
-
 package main
 
 // Helper functions to convert infix notation to RPN and calculates expression result.
@@ -29,36 +27,36 @@ parseLoop:
 		fmt.Printf("Lexem: %+v\n", ll)
 
 		switch {
-		case ll.Type == "NUMBER", ll.Type == "OPERATOR" && ll.Value == "!":
+		case ll.Type == NUMBER, ll.Type == OPERATOR && ll.Value == "!":
 			output = append(output, ll)
-		case ll.Type == "LP":
+		case ll.Type == LP:
 			stack.Push(ll)
-		case ll.Type == "RP":
+		case ll.Type == RP:
 			for {
 				cl := stack.Pop()
-				if cl.Type == "LP" {
+				if cl.Type == LP {
 					break
 				}
-				if cl.Type == unilex.LEOF {
+				if cl.Type == unilex.LexEOF {
 					log.Fatalf("No pair for parenthesis at %d", ll.Start)
 				}
 				output = append(output, cl)
 			}
-		case ll.Type == "OPERATOR":
+		case ll.Type == OPERATOR:
 			for {
-				if stack.Head().Type == "OPERATOR" && (opPriority[stack.Head().Value] > opPriority[ll.Value]) {
+				if stack.Head().Type == OPERATOR && (opPriority[stack.Head().Value] > opPriority[ll.Value]) {
 					output = append(output, stack.Pop())
 					continue
 				}
 				break
 			}
 			stack.Push(ll)
-		case ll.Type == unilex.LEOF:
+		case ll.Type == unilex.LexEOF:
 			break parseLoop
 		}
 	}
 
-	for stack.Head().Type != unilex.LEOF {
+	for stack.Head().Type != unilex.LexEOF {
 		output = append(output, stack.Pop())
 	}
 
@@ -68,26 +66,26 @@ parseLoop:
 func calculateRPN(rpnLexems []unilex.Lexem) string {
 	stack := lexemStack{}
 	for _, op := range rpnLexems {
-		if op.Type == "NUMBER" {
+		if op.Type == NUMBER {
 			stack.Push(op)
 		} else {
 			switch op.Value {
 			case "+":
 				a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
 				a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
-				stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2+a1, 'f', -1, 64)})
+				stack.Push(unilex.Lexem{Type: NUMBER, Value: strconv.FormatFloat(a2+a1, 'f', -1, 64)})
 			case "-":
 				a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
 				a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
-				stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2-a1, 'f', -1, 64)})
+				stack.Push(unilex.Lexem{Type: NUMBER, Value: strconv.FormatFloat(a2-a1, 'f', -1, 64)})
 			case "*":
 				a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
 				a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
-				stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2*a1, 'f', -1, 64)})
+				stack.Push(unilex.Lexem{Type: NUMBER, Value: strconv.FormatFloat(a2*a1, 'f', -1, 64)})
 			case "/":
 				a1, _ := strconv.ParseFloat(stack.Pop().Value, 64)
 				a2, _ := strconv.ParseFloat(stack.Pop().Value, 64)
-				stack.Push(unilex.Lexem{Type: "NUMBER", Value: strconv.FormatFloat(a2/a1, 'f', -1, 64)})
+				stack.Push(unilex.Lexem{Type: NUMBER, Value: strconv.FormatFloat(a2/a1, 'f', -1, 64)})
 			}
 		}
 	}
diff --git a/example/math_expression/stack.go b/example/math_expression/stack.go
index eebd476..5244f7c 100644
--- a/example/math_expression/stack.go
+++ b/example/math_expression/stack.go
@@ -1,6 +1,3 @@
-//go:build example
-// +build example
-
 package main
 
 // Simple lexem stack implementation.