Add integer dup and pop.

src/Push3Interpreter.sol

@@ -23,7 +23,9 @@ contract Push3Interpreter {
         NOOP,          // 0
         INTEGER_PLUS,  // 1
         INTEGER_MINUS, // 2
-        INTEGER_MULT   // 3
+        INTEGER_MULT,  // 3
+        INTEGER_DUP,   // 4
+        INTEGER_POP    // 5
     }
 
     // -----------------------------------------------------
@@ -202,6 +204,14 @@ contract Push3Interpreter {
                 temp[count] = makeInstruction(OpCode.INTEGER_MULT);
                 count++;
             }
+            else if (tokenType == 0x06) {
+                temp[count] = makeInstruction(OpCode.INTEGER_DUP);
+                count++;
+            }
+            else if (tokenType == 0x07) {
+                temp[count] = makeInstruction(OpCode.INTEGER_POP);
+                count++;
+            }
             else {
                 // unknown => NOOP
                 temp[count] = makeInstruction(OpCode.NOOP);
@@ -295,6 +305,18 @@ contract Push3Interpreter {
                         intTop++;
                     }
                 }
+                else if (op == OpCode.INTEGER_DUP) {
+                    if (intTop >= 1) {
+                        int256 a = intStack[intTop - 1];
+                        intStack[intTop] = a;
+                        intTop++;
+                    }
+                }
+                else if (op == OpCode.INTEGER_POP) {
+                    if (intTop >= 1) {
+                        intTop -= 1;
+                    }
+                }
             }
             else if (tag == CodeTag.INT_LITERAL) {
                 int32 val = extractInt32(topDesc);

test/Push3Interpreter.t.sol

@@ -174,6 +174,61 @@ contract Push3InterpreterTest is Test {
         assertEq(finalIntStack[0], 30, "Should be 10 * 3 = 30");
     }
 
+    function test_Dup() public view {
+
+        bytes memory code = hex"030006020000000A06";
+
+        uint256 sublistDesc = interpreter.makeDescriptor(
+            Push3Interpreter.CodeTag.SUBLIST,
+            0,  
+            9, 
+            0
+        );
+
+        uint256[] memory initCodeStack = new uint256[](0);
+        uint256[] memory initExecStack = new uint256[](1);
+        initExecStack[0] = sublistDesc;
+
+        int256[] memory initIntStack = new int256[](0);
+
+        // Run
+        (
+            ,
+            ,
+            int256[] memory finalIntStack
+        ) = interpreter.runInterpreter(code, initCodeStack, initExecStack, initIntStack);
+
+        assertEq(finalIntStack.length, 2, "finalIntStack should have length 1");
+        assertEq(finalIntStack[0], finalIntStack[1], "The top 2 values on the stack should be equal.");
+    }
+
+    function test_Pop() public view {
+
+        bytes memory code = hex"030006020000000A07";
+
+        uint256 sublistDesc = interpreter.makeDescriptor(
+            Push3Interpreter.CodeTag.SUBLIST,
+            0,  
+            9, 
+            0
+        );
+
+        uint256[] memory initCodeStack = new uint256[](0);
+        uint256[] memory initExecStack = new uint256[](1);
+        initExecStack[0] = sublistDesc;
+
+        int256[] memory initIntStack = new int256[](0);
+
+        // Run
+        (
+            ,
+            ,
+            int256[] memory finalIntStack
+        ) = interpreter.runInterpreter(code, initCodeStack, initExecStack, initIntStack);
+
+        assertEq(finalIntStack.length, 0, "finalIntStack should be empty");
+    }
+
     /**
      * @notice Test with an unknown token (0xF0).
      * We expect the parser to treat it as "unknown => NOOP"