ADD Implemented

elm.go

@@ -1,7 +1,94 @@
 package main
 
-import "fmt"
+import (
+	"fmt"
+	"os"
+	"errors"
+)
+
+const STACK_SIZE = 1024
+
+type Operation int
+
+const (
+	HALT Operation = 0
+	PUSH Operation = 1
+	ADD Operation = 2
+)
+
+type Instruction struct {
+	Operation Operation
+	Operand int
+}
+
+type Machine struct {
+	program []Instruction
+	stack []int
+	ip int
+	sp int
+	isHalted bool;
+}
+
+func Constructor() *Machine {
+	m := Machine{}
+	m.program = make([]Instruction, 0)
+	m.stack = make([]int, STACK_SIZE)
+	m.ip = 0
+	m.sp = 0
+	m.isHalted = false
+
+	return &m
+}
+
+func (m* Machine) Push(i Instruction) error {
+	m.program = append(m.program, i)
+	return nil
+}
+
+func (m* Machine) Execute() error {
+	instr := m.program[m.ip]
+	switch op := instr.Operation; op {
+	case HALT:
+		m.isHalted = true;
+	case PUSH:
+		m.stack[m.sp] = instr.Operand
+		m.sp++;
+		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++;
+	}
+	return nil
+}
+
+func (m* Machine) Print() {
+	fmt.Println("Stack:");
+	for i := 0; i <= m.sp; i++ {
+		fmt.Println(m.stack[i])
+	}
+}
 
 func main() {
-	fmt.Println("Hello, World!")
+	m := Constructor()
+
+	m.Push(Instruction{Operation: PUSH, Operand: 1})
+	m.Push(Instruction{Operation: PUSH, Operand: 2})
+	m.Push(Instruction{Operation: ADD})
+	m.Push(Instruction{Operation: HALT})
+	
+	for !m.isHalted {
+		m.Print()
+		err := m.Execute()
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "[ERR] %s", err);
+		}
+	}
+	m.Print()
 }