Implement codegen using an Observer

src/ast/PostfixObserver.cpp

@@ -0,0 +1,18 @@
+//
+// Created by christoph on 20.03.23.
+//
+
+#include "PostfixObserver.h"
+
+PostfixObserver::PostfixObserver(const Node &root) : Observer(root) {}
+
+// TODO: Shouldn't be recursive
+void PostfixObserver::traverse(const Node &node) {
+    for (const auto &child : node.getChildren()) {
+        depth++;
+        traverse(*child);
+        depth--;
+    }
+
+    action(node);
+}

src/ast/PostfixObserver.h

@@ -0,0 +1,23 @@
+//
+// Created by christoph on 20.03.23.
+//
+
+#ifndef LOGISIMASSEMBLER_POSTFIXOBSERVER_H
+#define LOGISIMASSEMBLER_POSTFIXOBSERVER_H
+
+#include "Observer.h"
+
+class PostfixObserver : public Observer {
+public:
+    PostfixObserver(const Node &root);
+
+    ~PostfixObserver() override = default;
+
+protected:
+    void traverse(const Node &node) override;
+
+protected:
+    uint32_t depth = 0;
+};
+
+#endif //LOGISIMASSEMBLER_PREFIXOBSERVER_H

src/codegen/CodegenObserver.cpp

@@ -0,0 +1,20 @@
+//
+// Created by christoph on 21.03.23.
+//
+
+#include "CodegenObserver.h"
+#include <boost/format.hpp>
+#include <iostream>
+
+CodegenObserver::CodegenObserver(const Node &node, std::string &output_string)
+        : PostfixObserver(node), output_string(output_string) {}
+
+void CodegenObserver::action(const Node &node) {
+    const uint8_t opcode = node.compile();
+    const uint8_t INVALID = -1;
+
+    if (opcode != INVALID) {
+        output_string += (boost::format("%x") % static_cast<uint32_t>(opcode)).str(); // uint8_t is always interpreted as char
+        output_string += ' ';
+    }
+}

src/codegen/CodegenObserver.h

@@ -0,0 +1,23 @@
+//
+// Created by christoph on 21.03.23.
+//
+
+#ifndef LOGISIMASSEMBLER_CODEGENOBSERVER_H
+#define LOGISIMASSEMBLER_CODEGENOBSERVER_H
+
+#include "../ast/PostfixObserver.h"
+
+class CodegenObserver : public PostfixObserver {
+public:
+    CodegenObserver(const Node &node, std::string &output_string);
+
+    ~CodegenObserver() override = default;
+
+protected:
+    void action(const Node &node) override;
+
+private:
+    std::string &output_string;
+};
+
+#endif //LOGISIMASSEMBLER_CODEGENOBSERVER_H