feat: introduce reference instruction

furvm/src/executor.cpp

@@ -102,6 +102,10 @@ void executor::step() {
     case instruction_t::Clone: {
         push_thing(std::move(thing()->clone()));
     } break;
+    case instruction_t::Reference: {
+        auto thing = pop_thing();
+        push_thing(std::move(thing->reference()));
+    } break;
     case instruction_t::Add: {
         auto rhs = pop_thing();
         auto lhs = pop_thing();

furvm/src/main.cpp

@@ -8,10 +8,11 @@
 #include <iostream>
 #include <memory>
 
-static constexpr std::array<furvm::byte, 8> s_bytecode = {
+static constexpr std::array<furvm::byte, 9> s_bytecode = {
     furvm::byte(furvm::instruction_t::PushB2I),
     67,
-    furvm::byte(furvm::instruction_t::Clone),
+    furvm::byte(furvm::instruction_t::Duplicate),
+    furvm::byte(furvm::instruction_t::Reference),
     furvm::byte(furvm::instruction_t::Add),
     furvm::byte(furvm::instruction_t::Call),
     1,