diff --git a/README.md b/README.md
index 1c48c9d..f53d353 100644
--- a/README.md
+++ b/README.md
@@ -40,6 +40,7 @@ Expr is a string expression parser in go. Not a fancy eval, just a simple and li
 - Float64 parses the given expr string into float64 as a result. e.g:
     - "2 + 2" -> 4
     - "2.2 + 2" -> 4.2
+    - "10 * -5 + (-5.5)" -> -55.5
 - Supported operators:
     - Arithmetic: [+, -, *, /]
 
@@ -56,12 +57,14 @@ Expr is a string expression parser in go. Not a fancy eval, just a simple and li
 - Int parses the given expr string into int as a result. e.g:
     - "2 + 2" -> 4
     - "2.2 + 2" -> 4
+    - "10 + ((-5 * -10) / -10) - 2" -> 3
 - Supported operators:
     - Arithmetic: [+, -, *, /, %]
     - Bitwise: [&, |, ^, &^, <<, >>] (signed integer)
 - Notes: 
     - << and >> operators are not permitted to be used in signed integer for go version less than 1.13.x.
     - Reference: [https://golang.org/doc/go1.13#language](https://golang.org/doc/go1.13#language)
+    - Even if bitwise is supported, the priority operation is not granted, any bit operation is advised to be put in parentheses.
 
 ```go
     str := "((2 * 2) * (8 + 2) * 2) + 2.56789"
diff --git a/boolean/boolean.go b/boolean/boolean.go
index be17d6c..2b6a2cf 100644
--- a/boolean/boolean.go
+++ b/boolean/boolean.go
@@ -15,6 +15,9 @@ var ErrUnsupportedOperator = errors.New("unsupported operator")
 // ErrInvalidOperationOnFloat is error invalid operation on float
 var ErrInvalidOperationOnFloat = errors.New("invalid operation on float")
 
+// ErrIntegerDividedByZero occurs when x/y and y equals to 0, Go does not allow integer to be devided by zero
+var ErrIntegerDividedByZero = errors.New("integer divide by zero")
+
 // Visitor is boolean visitor interface
 type Visitor interface {
 	Visit(node ast.Node) ast.Visitor
@@ -89,6 +92,10 @@ func (v *visitor) arithmetic(xVisitor, yVisitor *visitor, op token.Token) {
 	case token.MUL:
 		v.res, v.kind = fmt.Sprintf("%d", x*y), token.INT
 	case token.QUO:
+		if y == 0 {
+			v.err = ErrIntegerDividedByZero
+			return
+		}
 		v.res, v.kind = fmt.Sprintf("%d", x/y), token.INT
 	case token.REM:
 		v.res, v.kind = fmt.Sprintf("%d", x%y), token.INT
diff --git a/expr.go b/expr.go
index 337518b..872bb93 100644
--- a/expr.go
+++ b/expr.go
@@ -11,12 +11,17 @@ import (
 
 // Int parses the given expr string into int as a result.
 // - e.g:
-// 	-"2 + 2" -> 4
-// 	-"2.2 + 2" -> 4
+// 	- "2 + 2" -> 4
+// 	- "2.2 + 2" -> 4
+// 	- "10 + ((-5 * -10) / -10) - 2" -> 3
 //
 // - Supported operators:
 // 	- Arithmetic: [+, -, *, /, %]
 // 	- Bitwise: [&, |, ^, &^, <<, >>]
+// - Notes:
+//  - << and >> operators are not permitted to be used in signed integer for go version less than 1.13.x.
+//  - Reference: golang.org/doc/go1.13#language
+//  - Even if bitwise is supported, the priority operation is not granted, any bit operation is advised to be put in parentheses.
 func Int(str string) (int, error) {
 	expr, err := parser.ParseExpr(str)
 	if err != nil {
@@ -32,6 +37,7 @@ func Int(str string) (int, error) {
 // - e.g:
 // 	- "2 + 2" -> 4
 // 	- "2.2 + 2" -> 4.2
+//	- "10 * -5 + (-5.5)" -> -55.5
 //
 // - Supported operators:
 // 	- Arithmetic: [+, -, *, /]
diff --git a/expr_test.go b/expr_test.go
index 80c0d91..3b50f94 100644
--- a/expr_test.go
+++ b/expr_test.go
@@ -1,6 +1,7 @@
 package expr_test
 
 import (
+	"math"
 	"testing"
 
 	"github.com/muktihari/expr"
@@ -34,6 +35,17 @@ func TestInt(t *testing.T) {
 		{In: "((2 + 2) * 4 / 4) * 10 + 4.234567", Eq: 44},
 		{In: "((2 + 2) * 4 / 4) * 10.5 + 4.234567", Eq: 44},
 		{In: "((2 + 2) * 4 / 4) * 10.7 + 4.234567 * (50 + 50)", Eq: 440},
+		{In: "10 * -5", Eq: -50},
+		{In: "10 * (-5-5)", Eq: -100},
+		{In: "10 * -5 + (-5)", Eq: -55},
+		{In: "10 + (10 * -10)", Eq: -90},
+		{In: "10 + ((-5 * -10) * 10)", Eq: 510},
+		{In: "10 + ((-5 * -10) / -10) - 2", Eq: 3},
+		{In: "10 / 0", Eq: 0, Err: integer.ErrIntegerDividedByZero},
+		{In: "1100 | 0100", Eq: 12}, // = 1111
+		{In: "1100 ^ 0100", Eq: 8},  // = 1011
+		{In: "1100 & 0100", Eq: 4},  // = 0100
+		{In: "1100 &^ 0100", Eq: 8}, // = 1011
 	}
 
 	for _, tc := range tt {
@@ -75,6 +87,14 @@ func TestFloat64(t *testing.T) {
 		{In: "((2 + 2) * 4 / 4) * 10 + 4.234567", Eq: 44.234567},
 		{In: "((2 + 2) * 4 / 4) * 10.5 + 4.234567", Eq: 46.234567},
 		{In: "((2 + 2) * 4 / 4) * 10.7 + 4.234567 * (50 + 50)", Eq: 466.2567},
+		{In: "10 * -5", Eq: -50},
+		{In: "10 * (-5-5)", Eq: -100},
+		{In: "10 * -5 + (-5.5)", Eq: -55.5},
+		{In: "10 + (10 * -10)", Eq: -90},
+		{In: "10 + ((-5 * -10) * 10)", Eq: 510},
+		{In: "10 + ((-5 * -10) / -10) - 2", Eq: 3},
+		{In: "10 / 0", Eq: math.Inf(+1)},
+		{In: "0 / 10", Eq: 0},
 	}
 
 	for _, tc := range tt {
diff --git a/float/float.go b/float/float.go
index e38d20c..d014f40 100644
--- a/float/float.go
+++ b/float/float.go
@@ -26,6 +26,27 @@ type visitor struct {
 	err error
 }
 
+func (v *visitor) visitUnary(unaryExpr *ast.UnaryExpr) ast.Visitor {
+	switch unaryExpr.Op {
+	case token.ADD, token.SUB:
+		xVisitor := &visitor{}
+		ast.Walk(xVisitor, unaryExpr.X)
+		if xVisitor.err != nil {
+			v.err = xVisitor.err
+			return nil
+		}
+		switch unaryExpr.Op {
+		case token.ADD:
+			v.res = xVisitor.res
+		case token.SUB:
+			v.res = xVisitor.res * -1
+		}
+	default:
+		v.err = ErrUnsupportedOperator
+	}
+	return nil
+}
+
 func (v *visitor) visitBinary(binaryExpr *ast.BinaryExpr) ast.Visitor {
 	switch binaryExpr.Op {
 	case token.ADD, token.SUB, token.MUL, token.QUO:
@@ -70,6 +91,8 @@ func (v *visitor) Visit(node ast.Node) ast.Visitor {
 	switch d := node.(type) {
 	case *ast.ParenExpr:
 		return v.Visit(d.X)
+	case *ast.UnaryExpr:
+		return v.visitUnary(d)
 	case *ast.BinaryExpr:
 		return v.visitBinary(d)
 	case *ast.BasicLit:
diff --git a/integer/integer.go b/integer/integer.go
index 7417df5..19a822b 100644
--- a/integer/integer.go
+++ b/integer/integer.go
@@ -10,6 +10,9 @@ import (
 // ErrUnsupportedOperator is error unsupported operator
 var ErrUnsupportedOperator = errors.New("unsupported operator")
 
+// ErrIntegerDividedByZero occurs when x/y and y equals to 0, Go does not allow integer to be devided by zero
+var ErrIntegerDividedByZero = errors.New("integer divide by zero")
+
 // Visitor is integer visitor interface
 type Visitor interface {
 	Visit(node ast.Node) ast.Visitor
@@ -27,6 +30,27 @@ type visitor struct {
 	err  error
 }
 
+func (v *visitor) visitUnary(unaryExpr *ast.UnaryExpr) ast.Visitor {
+	switch unaryExpr.Op {
+	case token.ADD, token.SUB:
+		xVisitor := &visitor{}
+		ast.Walk(xVisitor, unaryExpr.X)
+		if xVisitor.err != nil {
+			v.err = xVisitor.err
+			return nil
+		}
+		switch unaryExpr.Op {
+		case token.ADD:
+			v.res = xVisitor.res
+		case token.SUB:
+			v.res = xVisitor.res * -1
+		}
+	default:
+		v.err = ErrUnsupportedOperator
+	}
+	return nil
+}
+
 func (v *visitor) arithmetic(binaryExpr *ast.BinaryExpr) {
 	x := &visitor{}
 	ast.Walk(x, binaryExpr.X)
@@ -49,6 +73,10 @@ func (v *visitor) arithmetic(binaryExpr *ast.BinaryExpr) {
 	case token.MUL:
 		v.res = x.res * y.res
 	case token.QUO:
+		if y.res == 0 {
+			v.err = ErrIntegerDividedByZero
+			return
+		}
 		v.res = x.res / y.res
 	case token.REM:
 		v.res = x.res % y.res
@@ -106,6 +134,8 @@ func (v *visitor) Visit(node ast.Node) ast.Visitor {
 	switch d := node.(type) {
 	case *ast.ParenExpr:
 		return v.Visit(d.X)
+	case *ast.UnaryExpr:
+		return v.visitUnary(d)
 	case *ast.BinaryExpr:
 		return v.visitBinary(d)
 	case *ast.BasicLit: