Other math implemented

elm.go

@@ -14,15 +14,18 @@ const (
 	HALT Operation = 0
 	PUSH Operation = 1
 	ADD Operation = 2
+	SUB Operation = 3
+	MUL Operation = 4
+	DIV Operation = 5
 )
 
-type Instruction struct {
+type Inst struct {
 	Operation Operation
 	Operand int
 }
 
 type Machine struct {
-	program []Instruction
+	program []Inst
 	stack []int
 	ip int
 	sp int
@@ -31,7 +34,7 @@ type Machine struct {
 
 func Constructor() *Machine {
 	m := Machine{}
-	m.program = make([]Instruction, 0)
+	m.program = make([]Inst, 0)
 	m.stack = make([]int, STACK_SIZE)
 	m.ip = 0
 	m.sp = 0
@@ -40,7 +43,7 @@ func Constructor() *Machine {
 	return &m
 }
 
-func (m* Machine) Push(i Instruction) error {
+func (m* Machine) Push(i Inst) error {
 	m.program = append(m.program, i)
 	return nil
 }
@@ -49,28 +52,58 @@ func (m* Machine) Execute() error {
 	instr := m.program[m.ip]
 	switch op := instr.Operation; op {
 	case HALT:
-		m.isHalted = true;
+		m.isHalted = true
 	case PUSH:
+		if (m.sp >= STACK_SIZE) {
+            return errors.New("Stack Overflow");
+        }
+
 		m.stack[m.sp] = instr.Operand
-		m.sp++;
+		m.sp++
-		m.ip++;
+		m.ip++
 	case ADD:
 		if (len(m.stack) < 2) {
 			return errors.New("Stack size is less than required to execute ADD")
 		}
-		m.sp--;
-		first := m.stack[m.sp]
-		m.stack[m.sp] = 0;
-		m.stack[m.sp - 1] = first + m.stack[m.sp - 1];
 		
-		m.ip++;
+		m.stack[m.sp - 2] += m.stack[m.sp - 1];
+		m.sp--
+		m.ip++
+	case SUB:
+		if (len(m.stack) < 2) {
+			return errors.New("Stack size is less than required to execute SUB")
+		}
+
+		m.stack[m.sp - 2] -= m.stack[m.sp - 1];
+		m.sp--
+		m.ip++
+	case MUL:
+		if (len(m.stack) < 2) {
+			return errors.New("Stack size is less than required to execute MUL")
+		}
+
+		m.stack[m.sp - 2] *= m.stack[m.sp - 1];
+		m.sp--
+		m.ip++
+	case DIV:
+		if (len(m.stack) < 2) {
+			return errors.New("Stack size is less than required to execute DIV")
+		}
+
+		if (m.stack[m.sp - 2] == 0 || m.stack[m.sp - 1] == 0) {
+			return errors.New("Divide by zero exception")
+		}
+
+		m.stack[m.sp - 2] /= m.stack[m.sp - 1];
+		m.sp--
+		m.ip++
 	}
 	return nil
 }
 
 func (m* Machine) Print() {
 	fmt.Println("Stack:");
-	for i := 0; i <= m.sp; i++ {
+	for i := 0; i < m.sp; i++ {
 		fmt.Println(m.stack[i])
 	}
 }
@@ -78,10 +111,16 @@ func (m* Machine) Print() {
 func main() {
 	m := Constructor()
 
-	m.Push(Instruction{Operation: PUSH, Operand: 1})
+	m.Push(Inst{Operation: PUSH, Operand: 1})
-	m.Push(Instruction{Operation: PUSH, Operand: 2})
+	m.Push(Inst{Operation: PUSH, Operand: 2})
-	m.Push(Instruction{Operation: ADD})
+	m.Push(Inst{Operation: ADD})
-	m.Push(Instruction{Operation: HALT})
+	m.Push(Inst{Operation: PUSH, Operand: 2})
+	m.Push(Inst{Operation: SUB})
+	m.Push(Inst{Operation: PUSH, Operand: 6})
+	m.Push(Inst{Operation: MUL})
+	m.Push(Inst{Operation: PUSH, Operand: 2})
+	m.Push(Inst{Operation: DIV})
+	m.Push(Inst{Operation: HALT})
 
 	for !m.isHalted {
 		m.Print()
@@ -90,5 +129,4 @@ func main() {
 			fmt.Fprintf(os.Stderr, "[ERR] %s", err);
 		}
 	}
-	m.Print()
 }