diff --git a/src/build/expression/Expression.go b/src/build/expression/Expression.go
index c2be790..7776c35 100644
--- a/src/build/expression/Expression.go
+++ b/src/build/expression/Expression.go
@@ -109,14 +109,10 @@ func (expr *Expression) write(builder *strings.Builder) {
 
 	builder.WriteByte('(')
 	builder.WriteString(expr.Token.Text())
-	builder.WriteByte(' ')
 
-	for i, child := range expr.Children {
+	for _, child := range expr.Children {
+		builder.WriteByte(' ')
 		child.write(builder)
-
-		if i != len(expr.Children)-1 {
-			builder.WriteByte(' ')
-		}
 	}
 
 	builder.WriteByte(')')
diff --git a/src/build/expression/Expression_test.go b/src/build/expression/Expression_test.go
index e267a60..eb992c6 100644
--- a/src/build/expression/Expression_test.go
+++ b/src/build/expression/Expression_test.go
@@ -118,6 +118,28 @@ func TestEachLeaf(t *testing.T) {
 	assert.Equal(t, err.Error(), "error")
 }
 
+func TestEachParameter(t *testing.T) {
+	src := []byte("1+2,3*4,5*6,7+8")
+	tokens := token.Tokenize(src)
+	parameters := []string{}
+
+	err := expression.EachParameter(tokens, func(parameter token.List) error {
+		expr := expression.Parse(parameter)
+		parameters = append(parameters, expr.String())
+		return nil
+	})
+
+	assert.Nil(t, err)
+	assert.DeepEqual(t, parameters, []string{"(+ 1 2)", "(* 3 4)", "(* 5 6)", "(+ 7 8)"})
+
+	err = expression.EachParameter(tokens, func(parameter token.List) error {
+		return fmt.Errorf("error")
+	})
+
+	assert.NotNil(t, err)
+	assert.Equal(t, err.Error(), "error")
+}
+
 func TestRemoveChild(t *testing.T) {
 	src := []byte("(1+2-3*4)+(5*6-7+8)")
 	tokens := token.Tokenize(src)
@@ -141,3 +163,17 @@ func TestNilGroup(t *testing.T) {
 	expr := expression.Parse(tokens)
 	assert.Nil(t, expr)
 }
+
+func TestInvalidOperator(t *testing.T) {
+	src := []byte("a +++ 2")
+	tokens := token.Tokenize(src)
+	expr := expression.Parse(tokens)
+	assert.Equal(t, expr.String(), "(+++ a 2)")
+}
+
+func TestInvalidOperatorCall(t *testing.T) {
+	src := []byte("+++()")
+	tokens := token.Tokenize(src)
+	expr := expression.Parse(tokens)
+	assert.NotNil(t, expr)
+}
diff --git a/src/build/expression/Operator.go b/src/build/expression/Operator.go
index 391ed74..5e50dc5 100644
--- a/src/build/expression/Operator.go
+++ b/src/build/expression/Operator.go
@@ -16,27 +16,29 @@ type Operator struct {
 // Operators defines the operators used in the language.
 // The number corresponds to the operator priority and can not be zero.
 var Operators = map[string]*Operator{
-	".":   {".", 13, 2},
-	"λ":   {"λ", 12, 1},
-	"!":   {"!", 11, 1},
-	"*":   {"*", 10, 2},
-	"/":   {"/", 10, 2},
-	"%":   {"%", 10, 2},
-	"+":   {"+", 9, 2},
-	"-":   {"-", 9, 2},
-	">>":  {">>", 8, 2},
-	"<<":  {"<<", 8, 2},
-	">":   {">", 7, 2},
-	"<":   {"<", 7, 2},
-	">=":  {">=", 7, 2},
-	"<=":  {"<=", 7, 2},
-	"==":  {"==", 6, 2},
-	"!=":  {"!=", 6, 2},
-	"&":   {"&", 5, 2},
-	"^":   {"^", 4, 2},
-	"|":   {"|", 3, 2},
-	"&&":  {"&&", 2, 2},
-	"||":  {"||", 1, 2},
+	".":  {".", 13, 2},
+	"λ":  {"λ", 12, 1},
+	"!":  {"!", 11, 1},
+	"*":  {"*", 10, 2},
+	"/":  {"/", 10, 2},
+	"%":  {"%", 10, 2},
+	"+":  {"+", 9, 2},
+	"-":  {"-", 9, 2},
+	">>": {">>", 8, 2},
+	"<<": {"<<", 8, 2},
+	"&":  {"&", 7, 2},
+	"^":  {"^", 6, 2},
+	"|":  {"|", 5, 2},
+
+	">":  {">", 4, 2},
+	"<":  {"<", 4, 2},
+	">=": {">=", 4, 2},
+	"<=": {"<=", 4, 2},
+	"==": {"==", 3, 2},
+	"!=": {"!=", 3, 2},
+	"&&": {"&&", 2, 2},
+	"||": {"||", 1, 2},
+
 	"=":   {"=", math.MinInt, 2},
 	":=":  {":=", math.MinInt, 2},
 	"+=":  {"+=", math.MinInt, 2},
@@ -56,7 +58,7 @@ func isComplete(expr *Expression) bool {
 		return true
 	}
 
-	if expr.Token.Kind == token.Operator && len(expr.Children) >= numOperands(expr.Token.Text()) {
+	if expr.Token.Kind == token.Operator && len(expr.Children) == numOperands(expr.Token.Text()) {
 		return true
 	}
 
diff --git a/src/build/scan.go b/src/build/scan.go
index 15fdfe9..93149b7 100644
--- a/src/build/scan.go
+++ b/src/build/scan.go
@@ -114,7 +114,7 @@ func scanFile(path string, functions chan<- *Function) error {
 				break
 			}
 
-			if tokens[i].Kind == token.NewLine {
+			if tokens[i].Kind == token.NewLine || tokens[i].Kind == token.Comment {
 				i++
 				continue
 			}
diff --git a/src/build/token/Tokenize.go b/src/build/token/Tokenize.go
index b2fc798..5388b4b 100644
--- a/src/build/token/Tokenize.go
+++ b/src/build/token/Tokenize.go
@@ -59,15 +59,24 @@ func Tokenize(buffer []byte) List {
 		// Comment
 		case '/':
 			if i+1 >= len(buffer) || buffer[i+1] != '/' {
-				tokens = append(tokens, Token{Operator, i, buffer[i : i+1]})
+				position := i
 				i++
+
+				for i < len(buffer) && isOperator(buffer[i]) {
+					i++
+				}
+
+				tokens = append(tokens, Token{Operator, position, buffer[position:i]})
 				continue
 			}
 
+			position := i
+
 			for i < len(buffer) && buffer[i] != '\n' {
 				i++
 			}
 
+			tokens = append(tokens, Token{Comment, position, buffer[position:i]})
 			continue
 
 		// String