diff --git a/tools/compiler/compiler.c b/tools/compiler/compiler.c
index 738763a..a909904 100644
--- a/tools/compiler/compiler.c
+++ b/tools/compiler/compiler.c
@@ -240,10 +240,7 @@ static void unary() {
 
   switch (operatorType) {
   case TOKEN_MINUS: {
-    code[cp++] = OP_PUSH_8;
-    code[cp++] = 0;
-    code[cp++] = OP_EXCH;
-    code[cp++] = OP_SUB_INT; // kinda cheating, should work
+    code[cp++] = OP_NEG;
     break;
   }
   case TOKEN_BANG: {
@@ -259,22 +256,85 @@ static void binary() {
   TokenType operatorType = parser.previous.type;
   ParseRule *rule = getRule(operatorType);
   parsePrecedence((Precedence)(rule->precedence + 1));
-
   switch (operatorType) {
   case TOKEN_PLUS: {
-    code[cp++] = OP_ADD_INT;
+    switch (parser.previous.type) {
+    case TOKEN_LITERAL_INT:
+      code[cp++] = OP_ADD_INT;
+      break;
+    case TOKEN_LITERAL_NAT:
+      code[cp++] = OP_ADD_NAT;
+      break;
+    case TOKEN_LITERAL_REAL:
+      code[cp++] = OP_ADD_REAL;
+      break;
+    case TOKEN_IDENTIFIER:
+      printf("FIXME: find the identifier's type for add\n");
+      break;
+    default:
+      printf("Unknown Add Arg=%d\n", parser.previous.type);
+      return; // Unreachable.
+    }
     break;
   }
   case TOKEN_MINUS: {
-    code[cp++] = OP_SUB_INT;
+    switch (parser.previous.type) {
+    case TOKEN_LITERAL_INT:
+      code[cp++] = OP_SUB_INT;
+      break;
+    case TOKEN_LITERAL_NAT:
+      code[cp++] = OP_SUB_NAT;
+      break;
+    case TOKEN_LITERAL_REAL:
+      code[cp++] = OP_SUB_REAL;
+      break;
+    case TOKEN_IDENTIFIER:
+      printf("FIXME: find the identifier's type for sub\n");
+      break;
+    default:
+      printf("Unknown Sub Arg=%d\n", parser.previous.type);
+      return; // Unreachable.
+    }
     break;
   }
   case TOKEN_STAR: {
-    code[cp++] = OP_MUL_INT;
+    switch (parser.previous.type) {
+    case TOKEN_LITERAL_INT:
+      code[cp++] = OP_MUL_INT;
+      break;
+    case TOKEN_LITERAL_NAT:
+      code[cp++] = OP_MUL_NAT;
+      break;
+    case TOKEN_LITERAL_REAL:
+      code[cp++] = OP_MUL_REAL;
+      break;
+    case TOKEN_IDENTIFIER:
+      printf("FIXME: find the identifier's type for mul\n");
+      break;
+    default:
+      printf("Unknown Mul Arg=%d\n", parser.previous.type);
+      return; // Unreachable.
+    }
     break;
   }
   case TOKEN_SLASH: {
-    code[cp++] = OP_DIV_INT;
+    switch (parser.previous.type) {
+    case TOKEN_LITERAL_INT:
+      code[cp++] = OP_DIV_INT;
+      break;
+    case TOKEN_LITERAL_NAT:
+      code[cp++] = OP_DIV_NAT;
+      break;
+    case TOKEN_LITERAL_REAL:
+      code[cp++] = OP_DIV_REAL;
+      break;
+    case TOKEN_IDENTIFIER:
+      printf("FIXME: find the identifier's type for div\n");
+      break;
+    default:
+      printf("Unknown Div Arg=%d\n", parser.previous.type);
+      return; // Unreachable.
+    }
     break;
   }
   case TOKEN_EQ_EQ: {
diff --git a/vm/vm.c b/vm/vm.c
index cda8997..ea3a8dc 100644
--- a/vm/vm.c
+++ b/vm/vm.c
@@ -389,6 +389,11 @@ bool step_vm() {
     stack[sp++] = result;
     return true;
   }
+  case OP_NEG: {
+    i32 a = (i32)stack[--sp];
+    stack[sp++] = -a;
+    return true;
+  }  
   case OP_NOT: {
     u32 a = !stack[--sp];
     stack[sp++] = a;
diff --git a/vm/vm.h b/vm/vm.h
index 7656e88..3017631 100644
--- a/vm/vm.h
+++ b/vm/vm.h
@@ -60,6 +60,7 @@ typedef enum {
   OP_BIT_AND,           /* obj2 obj1 `bit_and` obj             | obj1 & obj2 */
   OP_BIT_OR,            /* obj2 obj1 `bit_or`  obj             | obj1 | obj2 */
   OP_BIT_XOR,           /* obj2 obj1 `bit_xor` obj             | obj1 ^ obj2 */
+  OP_NEG,               /* obj1 `neg` -obj                     | -obj1 */
   OP_NOT,               /* obj1 `bit_xor` !obj                 | not obj1 */
   OP_JMP,               /* pc `jump`                           | jump unconditionally */
   OP_JMP_FLAG,          /* pc `jump_if_flag`                   | jump to pc if flag > 0 */