From 6c3eb9c159db4919e1aa2326d3052f3df288c3d8 Mon Sep 17 00:00:00 2001
From: Daniel Zhu <danielfangzhu@gmail.com>
Date: Mon, 9 Nov 2020 20:21:30 -0800
Subject: [PATCH] Added activation records!

---
 Interpreter/Stack.h       | 38 ++++++++++++++++++++++++++++++++++++++
 Interpreter/interpreter.h | 26 +++++++++++++++++---------
 2 files changed, 55 insertions(+), 9 deletions(-)
 create mode 100644 Interpreter/Stack.h

diff --git a/Interpreter/Stack.h b/Interpreter/Stack.h
new file mode 100644
index 0000000..c19d9f6
--- /dev/null
+++ b/Interpreter/Stack.h
@@ -0,0 +1,38 @@
+#pragma once
+#include <string>
+#include <variant>
+#include <map>
+#include <vector>
+enum class ARType {
+	PROGRAM
+};
+using value = std::variant<int, double, std::string>;
+class ActivationRecord {
+public:
+	std::string name;
+	ARType type;
+	int nesting_level;
+	std::map<std::string, value> members;
+	ActivationRecord(ARType type, int nesting_level, std::string name = "") {
+		this->name = name;
+		this->type = type;
+		this->nesting_level = nesting_level;
+		this->members = members;
+	}
+	value& operator [] (std::string index) {
+		return members[index];
+	}
+};
+class CallStack {
+public:
+	std::vector<ActivationRecord> records;
+	void push(ActivationRecord& ar) {
+		records.push_back(ar);
+	}
+	void pop() {
+		records.pop_back();
+	}
+	ActivationRecord& peek() {
+		return records.back();
+	}
+};
\ No newline at end of file
diff --git a/Interpreter/interpreter.h b/Interpreter/interpreter.h
index 7b817c1..4fbec4e 100644
--- a/Interpreter/interpreter.h
+++ b/Interpreter/interpreter.h
@@ -7,6 +7,7 @@
 #include <typeinfo>
 #include <variant>
 #include <cassert>
+#include "./Stack.h"
 namespace interpreter {
 	class Interpreter
 	{
@@ -15,7 +16,7 @@ namespace interpreter {
 		ScopedSymbolTable symTab;
 		ScopedSymbolTable& currentSymTab = symTab;
 	public:
-		std::map<std::string, std::variant<int, double, std::string>> GLOBAL_SCOPE;
+		CallStack stack;
 		Interpreter(std::string input) : parser(input), symTab("global", 1) {
 
 		}
@@ -192,16 +193,18 @@ namespace interpreter {
 		void visit_Assign(class Assign assign) {
 			std::string var_name = assign.var.value;
 			std::string type = symTab.lookup(var_name)->type->name;
+			ActivationRecord& ar = stack.peek();
 			if (type == "int") {
-				GLOBAL_SCOPE[var_name] = visit<int>(assign.right);
+				ar[var_name] = visit<int>(assign.right);
 				return;
 			}
 			else if (type == "real") {
-				GLOBAL_SCOPE[var_name] = visit<double>(assign.right);
+				ar[var_name] = visit<double>(assign.right);
 				return;
 			}
 			else if (type == "string") {
-				GLOBAL_SCOPE[var_name] = visit_String(*static_cast<String*>(assign.right));
+				ar[var_name] = visit_String(*static_cast<String*>(assign.right));
+				return;
 			}
 			else {
 				std::string error("Var type not supported");
@@ -210,10 +213,11 @@ namespace interpreter {
 		}
 		template<class T>
 		T visit_Var(Var var) {
-			if (GLOBAL_SCOPE.find(var.value) != GLOBAL_SCOPE.end()) {
+			ActivationRecord& ar = stack.peek();
+			if (ar.members.find(var.value) != ar.members.end()) {
 				if constexpr (std::is_same_v<T, int>) {
 					std::string type = symTab.lookup(var.value)->type->name;
-					if (type == "int") return (T)std::get<int>(GLOBAL_SCOPE[var.value]);
+					if (type == "int") return (T)std::get<int>(ar[var.value]);
 					else {
 						std::string error("Wanted integer, got " + type);
 						throw error;
@@ -221,9 +225,9 @@ namespace interpreter {
 				}
 				else if constexpr (std::is_same_v<T, double>) {
 					std::string type = symTab.lookup(var.value)->type->name;
-					if (type == "real") return (T)std::get<double>(GLOBAL_SCOPE[var.value]);
+					if (type == "real") return (T)std::get<double>(ar[var.value]);
 					else if (type == "int") {
-						return (T)std::get<int>(GLOBAL_SCOPE[var.value]);
+						return (T)std::get<int>(ar[var.value]);
 					}
 					else {
 						std::string error("Wanted real, got " + type);
@@ -232,7 +236,7 @@ namespace interpreter {
 				}
 				else if constexpr (std::is_same_v<T, std::string>) {
 					std::string type = symTab.lookup(var.value)->type->name;
-					if (type == "string") return std::get<std::string>(GLOBAL_SCOPE[var.value]);
+					if (type == "string") return std::get<std::string>(ar[var.value]);
 					else {
 						std::string error("Wanted string, got " + type);
 						throw error;
@@ -270,7 +274,11 @@ namespace interpreter {
 			//std::cout << "Finished building symtab...\n";
 			symTab = symtabBuilder.currentScope;
 			//std::cout << "Interpreting...\n";
+			ARType t = ARType::PROGRAM;
+			ActivationRecord ar(t, 1);
+			stack.push(ar);
 			visit_Block(p.block);
+			stack.pop();
 		}
 	};
 }
\ No newline at end of file