Add block statements

.gitignore

@@ -1,3 +1,5 @@
 cclox
 clox
 *.dSYM
+.vscode
+.zed

Makefile

@@ -13,7 +13,7 @@ CLOX_OUT  = clox
 all: cclox clox
 
 cclox: ${CCLOX_SRC}
-	${CXX} ${CFLAGS} ${CCLOX_SRC} -o ${CCLOX_OUT}
+	${CXX} -std=c++20 ${CFLAGS} ${CCLOX_SRC} -o ${CCLOX_OUT}
 
 clox: ${CLOX_SRC}
 	${CC} ${CFLAGS} ${CLOX_SRC} -o ${CLOX_OUT}

cclox_src/error_handler.cc

@@ -1,10 +1,24 @@
 #include "error_handler.hh"
+#include "tokenizer.hh"
 #include <iostream>
 
 void ErrorHandler::error(int line, const std::string &message) {
   report(line, "", message);
 }
 
+void ErrorHandler::error(Token token, const std::string &message) {
+  if (token.type == TokenType::EOFILE) {
+    report(token.line, " at end", message);
+  } else {
+    report(token.line, " at '" + token.lexeme + "'", message);
+  }
+}
+
+void ErrorHandler::runtime_error(const RuntimeException &exception) {
+  std::cout << "RuntimeException [" << exception.token.line << "]: " << exception.what() << '\n';
+  had_runtime_error = true;
+}
+
 void ErrorHandler::report(int line, const std::string &where, const std::string &message) {
   std::cout << "[line " << line << "] Error" << where << ": " << message << '\n';
   had_error = true;

cclox_src/error_handler.hh

@@ -1,14 +1,30 @@
 #ifndef ERROR_HANDLER_HH
 #define ERROR_HANDLER_HH
 
+#include "tokenizer.hh"
+#include <exception>
 #include <string>
 
+struct RuntimeException : public std::exception {
+  RuntimeException(Token token, const std::string& message) : token{token}, message{message} {}
+  const char* what() const noexcept override {
+    return message.c_str();
+  }
+
+  Token token;
+private:
+  std::string message;
+};
+
 struct ErrorHandler {
   ErrorHandler() : had_error{false} {};
   void error(int line, const std::string &message);
+  void error(Token token, const std::string &message);
+  void runtime_error(const RuntimeException &exception);
   void report(int line, const std::string &where, const std::string &message);
 
   bool had_error;
+  bool had_runtime_error;
 };
 
 #endif

cclox_src/interpreter.cc

@@ -1,6 +1,8 @@
 #include "interpreter.hh"
 #include "error_handler.hh"
 #include "tokenizer.hh"
+#include "parser.hh"
+#include <vector>
 #include <cstdint>
 #include <fstream>
 #include <iostream>
@@ -33,6 +35,9 @@ void run_file(const char *path) {
     if (error_handler.had_error) {
       exit(EX_DATAERR);
     }
+    if (error_handler.had_runtime_error) {
+      exit(EX_SOFTWARE);
+    }
   }
 }
 
@@ -43,6 +48,7 @@ void run_prompt() {
     run(line);
     std::cout << PROMPT;
     error_handler.had_error = false;
+    error_handler.had_runtime_error = false;
   }
 }
 
@@ -50,7 +56,13 @@ void run(const std::string &code) {
   Scanner scanner{code};
   std::vector<Token> tokens = scanner.scan_tokens();
 
-  for (const auto &token : tokens) {
-    std::cout << token << '\n';
+  Parser parser{tokens};
+  std::vector<Stmt> statements = parser.parse();
+
+  if (error_handler.had_error) {
+    return;
   }
+
+  static AstInterpreter interpreter{};
+  interpreter.interpret(statements);
 }

cclox_src/main.cc

@@ -8,27 +8,12 @@
 ErrorHandler error_handler{};
 
 int main(int argc, char *argv[]) {
-  (void)argc;
-  (void)argv;
-  // if (argc > 2) {
-  //   std::cout << "Usage: cclox [script]\n";
-  //   exit(EX_USAGE);
-  // }
-  //
-  // run_interpreter(argc, argv);
+  if (argc > 2) {
+    std::cout << "Usage: cclox [script]\n";
+    exit(EX_USAGE);
+  }
 
-  ExprPtr literal = std::make_shared<Expr>(ExprType::LITERAL, Literal{123});
-  ExprPtr left = std::make_shared<Expr>(ExprType::UNARY, Unary{Token{TokenType::MINUS, "-", Object{}, 1}, literal});
-
-  Token op{TokenType::STAR, "*", Object{}, 1};
-
-  ExprPtr gliteral = std::make_shared<Expr>(ExprType::LITERAL, Literal{45.67});
-  ExprPtr right = std::make_shared<Expr>(ExprType::GROUPING, gliteral);
-
-  Expr expr = {ExprType::BINARY, Binary{left, op, right}};
-
-  AstPrinter printer{};
-  std::cout << printer.print(expr) << '\n';
+  run_interpreter(argc, argv);
 
   return 0;
 }

cclox_src/parser.cc

@@ -1,6 +1,11 @@
-#ifndef PARSER_CC
-#define PARSER_CC
+#ifndef MAIN_PARSER_CC
+#define MAIN_PARSER_CC
 
 #include "parser/expr.cc"
+#include "parser/stmt.cc"
+#include "parser/parser.cc"
+#include "parser/environment.cc"
+#include "parser/ast_printer.cc"
+#include "parser/ast_interpreter.cc"
 
 #endif

cclox_src/parser.hh

@@ -1,6 +1,11 @@
-#ifndef PARSER_HH
-#define PARSER_HH
+#ifndef MAIN_PARSER_HH
+#define MAIN_PARSER_HH
 
 #include "parser/expr.hh"
+#include "parser/stmt.hh"
+#include "parser/parser.hh"
+#include "parser/environment.hh"
+#include "parser/ast_printer.hh"
+#include "parser/ast_interpreter.hh"
 
 #endif

cclox_src/parser/ast_interpreter.cc

@@ -0,0 +1,242 @@
+#include "ast_interpreter.hh"
+#include "environment.hh"
+#include "expr.hh"
+#include "stmt.hh"
+#include "../error_handler.hh"
+#include "../tokenizer.hh"
+#include <exception>
+#include <memory>
+#include <string>
+#include <vector>
+#include <cassert>
+#include <iostream>
+
+extern ErrorHandler error_handler;
+
+void AstInterpreter::interpret(const std::vector<Stmt> &statements) {
+  try {
+    for (const Stmt & stmt : statements) {
+      execute(stmt);
+    }
+  } catch (RuntimeException e) {
+    error_handler.runtime_error(e);
+  }
+}
+
+void AstInterpreter::execute(const Stmt &stmt) {
+  switch (stmt.type) {
+    case StmtType::EXPRESSION: return execute_expression_statement(stmt);
+    case StmtType::PRINT:      return execute_print_statement(stmt);
+    case StmtType::VAR:        return execute_var_statement(stmt);
+    case StmtType::BLOCK: {
+      std::shared_ptr<_Block> ptr = std::get<std::shared_ptr<_Block>>(stmt.value);
+      assert(ptr != nullptr);
+      return execute_block_statement(ptr->statements, Environment{std::make_shared<Environment>(environment)});
+    }
+  }
+}
+
+void AstInterpreter::execute_expression_statement(const Stmt &stmt) {
+  std::shared_ptr<_Expression> ptr = std::get<std::shared_ptr<_Expression>>(stmt.value);
+  assert(ptr != nullptr);
+  evaluate(ptr->expr);
+}
+
+void AstInterpreter::execute_print_statement(const Stmt &stmt) {
+  std::shared_ptr<_Print> ptr = std::get<std::shared_ptr<_Print>>(stmt.value);
+  assert(ptr != nullptr);
+  Object value{evaluate(ptr->expr)};
+  std::cout << value << '\n';
+}
+
+void AstInterpreter::execute_var_statement(const Stmt &stmt) {
+  Object value{};
+  std::shared_ptr<_Var> ptr = std::get<std::shared_ptr<_Var>>(stmt.value);
+  assert(ptr != nullptr);
+
+  if (ptr->expr.type == ExprType::LITERAL) {
+    std::shared_ptr<_Literal> eptr = std::get<std::shared_ptr<_Literal>>(ptr->expr.value);
+    assert(eptr != nullptr);
+    if (eptr->value.type == ObjectType::NIL) {
+      environment.define(ptr->name.lexeme, value);
+      return;
+    }
+  }
+
+  value = evaluate(ptr->expr);
+  environment.define(ptr->name.lexeme, value);
+}
+
+void AstInterpreter::execute_block_statement(const std::vector<Stmt> &statements, Environment environment) {
+  Environment previous = this->environment;
+
+  try {
+    this->environment = environment;
+    for (const auto &stmt : statements) {
+      execute(stmt);
+    }
+  } catch (std::exception) {}
+
+  this->environment = previous;
+}
+
+Object AstInterpreter::evaluate(const Expr &expr) {
+  switch (expr.type) {
+    case ExprType::BINARY:   return evaluate_binary_expression(expr);
+    case ExprType::GROUPING: return evaluate_grouping_expression(expr);
+    case ExprType::LITERAL:  return evaluate_literal_expression(expr);
+    case ExprType::UNARY:    return evaluate_unary_expression(expr);
+    case ExprType::VARIABLE: return evaluate_variable_expression(expr);
+    case ExprType::ASSIGN:   return evaluate_assignment_expression(expr);
+  }
+}
+
+Object AstInterpreter::evaluate_binary_expression(const Expr &expr) {
+  std::shared_ptr<_Binary> ptr = std::get<std::shared_ptr<_Binary>>(expr.value);
+  assert(ptr != nullptr);
+
+  Object left  = evaluate(ptr->left);
+  Object right = evaluate(ptr->right);
+
+  if (left.type == ObjectType::NUMBER && right.type == ObjectType::NUMBER) {
+    double left_val = std::get<double>(left.value);
+    double right_val = std::get<double>(right.value);
+
+    switch (ptr->op.type) {
+      case TokenType::PLUS:  return left_val + right_val;
+      case TokenType::MINUS: return left_val - right_val;
+      case TokenType::STAR:  return left_val * right_val;
+      case TokenType::SLASH: {
+        if (right_val == 0) {
+          throw RuntimeException{ptr->op, "Division by zero."};
+        }
+        return left_val / right_val;
+      }
+
+      case TokenType::GREATER:       return left_val > right_val;
+      case TokenType::GREATER_EQUAL: return left_val >= right_val;
+      case TokenType::LESS:          return left_val < right_val;
+      case TokenType::LESS_EQUAL:    return left_val <= right_val;
+
+      case TokenType::BANG_EQUAL:  return left_val != right_val;
+      case TokenType::EQUAL_EQUAL: return left_val == right_val;
+
+      default: throw RuntimeException{ptr->op, "Operator " + ptr->op.lexeme + " is not supported for numbers."};
+    }
+  }
+
+  if (left.type == ObjectType::STRING_LIT) {
+    right = Object{StringObjectType::LITERAL, right.to_string()};
+  }
+
+  if (right.type == ObjectType::STRING_LIT) {
+    left = Object{StringObjectType::LITERAL, left.to_string()};
+  }
+
+  if (left.type == ObjectType::STRING_LIT && right.type == ObjectType::STRING_LIT) {
+    std::string left_val = std::get<std::string>(left.value);
+    std::string right_val = std::get<std::string>(right.value);
+
+    switch (ptr->op.type) {
+      case TokenType::PLUS: return Object{StringObjectType::LITERAL, left_val + right_val};
+
+      case TokenType::BANG_EQUAL:  return left_val != right_val;
+      case TokenType::EQUAL_EQUAL: return left_val == right_val;
+
+      default: throw RuntimeException{ptr->op, "Operator " + ptr->op.lexeme + " is not supported for strings."};
+    }
+  }
+
+  if (left.type == ObjectType::BOOL && right.type == ObjectType::BOOL) {
+    bool left_val = std::get<bool>(left.value);
+    bool right_val = std::get<bool>(right.value);
+
+    switch (ptr->op.type) {
+      case TokenType::BANG_EQUAL:  return left_val != right_val;
+      case TokenType::EQUAL_EQUAL: return left_val == right_val;
+
+      default: throw RuntimeException{ptr->op, "Operator " + ptr->op.lexeme + " is not supported for booleans."};
+    }
+  }
+
+  if (left.type == ObjectType::NIL && right.type == ObjectType::NIL) {
+    switch (ptr->op.type) {
+      case TokenType::BANG_EQUAL:  return false;
+      case TokenType::EQUAL_EQUAL: return true;
+
+      default: throw RuntimeException{ptr->op, "Operator " + ptr->op.lexeme + " is not supported for null."};
+    }
+  }
+
+  if (left.type == ObjectType::NIL) {
+    switch (ptr->op.type) {
+      case TokenType::BANG_EQUAL:  return true;
+      case TokenType::EQUAL_EQUAL: return false;
+
+      default: break;
+    }
+  }
+
+  throw RuntimeException{ptr->op, "Operator " + ptr->op.lexeme + " is not supported for operands " + left.to_string() + " and " + right.to_string() + "."};
+}
+
+Object AstInterpreter::evaluate_grouping_expression(const Expr &expr) {
+  std::shared_ptr<_Grouping> ptr = std::get<std::shared_ptr<_Grouping>>(expr.value);
+  assert(ptr != nullptr);
+  return evaluate(ptr->expr);
+}
+
+Object AstInterpreter::evaluate_literal_expression(const Expr &expr) {
+  std::shared_ptr<_Literal> ptr = std::get<std::shared_ptr<_Literal>>(expr.value);
+  assert(ptr != nullptr);
+  return ptr->value;
+}
+
+Object AstInterpreter::evaluate_unary_expression(const Expr &expr) {
+  std::shared_ptr<_Unary> ptr = std::get<std::shared_ptr<_Unary>>(expr.value);
+  assert(ptr != nullptr);
+
+  Object right = evaluate(ptr->right);
+
+  switch (ptr->op.type) {
+    case TokenType::MINUS: {
+      switch (right.type) {
+        case ObjectType::NUMBER: {
+          double value = std::get<double>(right.value);
+          return -value;
+        }
+        default: throw RuntimeException{ptr->op, "Operand to unary operator - must be a number."};
+      }
+    }
+    case TokenType::BANG:
+      return !is_truthy(right);
+    default: break;
+  }
+
+  return Object{};
+}
+
+Object AstInterpreter::evaluate_variable_expression(const Expr &expr) {
+  std::shared_ptr<_Variable> ptr = std::get<std::shared_ptr<_Variable>>(expr.value);
+  assert(ptr != nullptr);
+  return environment.get(ptr->name);
+}
+
+Object AstInterpreter::evaluate_assignment_expression(const Expr &expr) {
+  std::shared_ptr<_Assign> ptr = std::get<std::shared_ptr<_Assign>>(expr.value);
+  assert(ptr != nullptr);
+  Object value = evaluate(ptr->value);
+  environment.assign(ptr->name, value);
+  return value;
+}
+
+bool AstInterpreter::is_truthy(const Object &object) {
+  switch (object.type) {
+    case ObjectType::NIL: return false;
+    case ObjectType::BOOL: {
+      bool value = std::get<bool>(object.value);
+      return value;
+    }
+    default: return true;
+  }
+}

cclox_src/parser/ast_interpreter.hh

@@ -0,0 +1,33 @@
+#ifndef AST_INTERPRETER_HH
+#define AST_INTERPRETER_HH
+
+#include "expr.hh"
+#include "stmt.hh"
+#include "environment.hh"
+#include "../tokenizer.hh"
+#include <vector>
+
+struct AstInterpreter {
+  void interpret(const std::vector<Stmt> &statements);
+
+private:
+  void execute(const Stmt &stmt);
+  void execute_expression_statement(const Stmt &stmt);
+  void execute_print_statement(const Stmt &stmt);
+  void execute_var_statement(const Stmt &stmt);
+  void execute_block_statement(const std::vector<Stmt> &statements, Environment environment);
+
+  Object evaluate(const Expr &expr);
+  Object evaluate_binary_expression(const Expr &expr);
+  Object evaluate_grouping_expression(const Expr &expr);
+  Object evaluate_literal_expression(const Expr &expr);
+  Object evaluate_unary_expression(const Expr &expr);
+  Object evaluate_variable_expression(const Expr &expr);
+  Object evaluate_assignment_expression(const Expr &expr);
+  bool is_truthy(const Object &object);
+  bool is_equal(const Object &left, const Object &right);
+
+  Environment environment{};
+};
+
+#endif

cclox_src/parser/ast_printer.cc

@@ -0,0 +1,51 @@
+#include "ast_printer.hh"
+#include "expr.hh"
+#include <cassert>
+#include <string>
+#include <sstream>
+
+std::string AstPrinter::print(const Expr &expr) {
+  switch (expr.type) {
+    case ExprType::BINARY: {
+      std::shared_ptr<_Binary> ptr = std::get<std::shared_ptr<_Binary>>(expr.value);
+      assert(ptr != nullptr);
+      return parenthesize(ptr->op.lexeme, {&ptr->left, &ptr->right});
+    }
+    case ExprType::GROUPING: {
+      std::shared_ptr<_Grouping> ptr = std::get<std::shared_ptr<_Grouping>>(expr.value);
+      assert(ptr != nullptr);
+      return parenthesize("group", {&ptr->expr});
+    }
+    case ExprType::LITERAL: {
+      std::shared_ptr<_Literal> ptr = std::get<std::shared_ptr<_Literal>>(expr.value);
+      assert(ptr != nullptr);
+      return ptr->value.to_string();
+    }
+    case ExprType::UNARY: {
+      std::shared_ptr<_Unary> ptr = std::get<std::shared_ptr<_Unary>>(expr.value);
+      assert(ptr != nullptr);
+      return parenthesize(ptr->op.lexeme, {&ptr->right});
+    }
+    case ExprType::VARIABLE: {
+      std::shared_ptr<_Variable> ptr = std::get<std::shared_ptr<_Variable>>(expr.value);
+      assert(ptr != nullptr);
+      return ptr->name.lexeme;
+    }
+    case ExprType::ASSIGN: {
+      std::shared_ptr<_Assign> ptr = std::get<std::shared_ptr<_Assign>>(expr.value);
+      assert(ptr != nullptr);
+      return ptr->name.lexeme;
+    }
+  }
+}
+
+std::string AstPrinter::parenthesize(const std::string &name, std::vector<const Expr *> exprs) {
+  std::stringstream ss{};
+  ss << '(' << name;
+  for (const Expr *expr : exprs) {
+    ss << ' ' << print(*expr);
+  }
+  ss << ')';
+
+  return ss.str();
+}

cclox_src/parser/ast_printer.hh

@@ -0,0 +1,13 @@
+#ifndef AST_PRINTER_HH
+#define AST_PRINTER_HH
+
+#include "expr.hh"
+#include <string>
+
+struct AstPrinter {
+  std::string print(const Expr &expr);
+private:
+  std::string parenthesize(const std::string &name, std::vector<const Expr *> exprs);
+};
+
+#endif

cclox_src/parser/environment.cc

@@ -0,0 +1,64 @@
+#include "environment.hh"
+#include "../error_handler.hh"
+#include <algorithm>
+#include <memory>
+#include <utility>
+
+Environment::Environment(const Environment &other) : enclosing{other.enclosing}, values{other.values} {}
+
+Environment::Environment(Environment &&other) noexcept 
+  : enclosing{std::move(other.enclosing)}, values{std::move(other.values)} {}
+
+Environment &Environment::operator=(const Environment &other) {
+  if (this == &other) {
+    return *this;
+  }
+
+  enclosing = other.enclosing;
+  values    = other.values;
+
+  return *this;
+}
+
+Environment &Environment::operator=(Environment &&other) noexcept {
+  if (this == &other) {
+    return *this;
+  }
+
+  enclosing = std::move(other.enclosing);
+  values    = std::move(other.values);
+
+  other.enclosing.reset();
+
+  return *this;
+}
+
+void Environment::define(const std::string &name, const Object &value) {
+  values.insert(std::pair(name, value));
+}
+
+void Environment::assign(const Token &name, const Object &value) {
+  if (values.find(name.lexeme) != values.end()) {
+    values.at(name.lexeme) = value;
+    return;
+  }
+
+  if (enclosing != nullptr) {
+    enclosing->assign(name, value);
+    return;
+  }
+
+  throw RuntimeException(name, "Undefined variable '" + name.lexeme + "'.");
+}
+
+Object Environment::get(const Token &name) {
+  if (values.find(name.lexeme) != values.end()) {
+    return values.at(name.lexeme);
+  }
+
+  if (enclosing != nullptr) {
+    return enclosing->get(name);
+  }
+
+  throw RuntimeException(name, "Undefined variable '" + name.lexeme + "'.");
+}

cclox_src/parser/environment.hh

@@ -0,0 +1,28 @@
+#ifndef ENVIRONMENT_HH
+#define ENVIRONMENT_HH
+
+#include "../tokenizer.hh"
+#include <memory>
+#include <string>
+#include <unordered_map>
+
+struct Environment {
+  Environment() : enclosing{nullptr}, values{} {}
+  Environment(std::shared_ptr<Environment> enclosing) : enclosing{enclosing}, values{} {}
+  Environment(const Environment &other);
+  Environment(Environment &&other) noexcept;
+
+  Environment &operator=(const Environment &other);
+  Environment &operator=(Environment &&other) noexcept;
+
+  ~Environment() = default;
+
+  void define(const std::string &name, const Object &value);
+  void assign(const Token &name, const Object &value);
+  Object get(const Token &name);
+private:
+  std::shared_ptr<Environment> enclosing;
+  std::unordered_map<std::string, Object> values;
+};
+
+#endif

cclox_src/parser/expr.cc

@@ -1,53 +1,35 @@
 #include "expr.hh"
 #include "../tokenizer.hh"
-#include <cassert>
-#include <string>
-#include <vector>
-#include <sstream>
+#include <utility>
 
-std::string AstPrinter::print(const Expr &expr) {
-  switch (expr.type) {
-    case ExprType::BINARY: {
-      Binary node = std::get<Binary>(expr.value);
-      assert(node.left != NULL && node.right != NULL);
-      return parenthesize(node.op.lexeme, {*node.left, *node.right});
-    }
-    case ExprType::GROUPING: {
-      Grouping node = std::get<Grouping>(expr.value);
-      assert(node.expression != NULL);
-      return parenthesize("group", {*node.expression});
-    }
-    case ExprType::LITERAL: {
-      Literal node = std::get<Literal>(expr.value);
-      switch (node.value.type) {
-        case ObjectType::NIL:
-          return "nil";
-        case ObjectType::IDENTIFIER:
-        case ObjectType::STRING_LIT: {
-          std::string value = std::get<std::string>(node.value.value);
-          return value;
-        }
-        case ObjectType::NUMBER: {
-          double value = std::get<double>(node.value.value);
-          return std::to_string(value);
-        }
-      }
-    }
-    case ExprType::UNARY: {
-      Unary node = std::get<Unary>(expr.value);
-      assert(node.right != NULL);
-      return parenthesize(node.op.lexeme, {*node.right});
-    }
+Expr::Expr(ExprType type, ExprVariant value) : type{type}, value{value} {}
+
+// Copy constructor
+Expr::Expr(const Expr &other) : type{other.type}, value{other.value} {}
+
+// Move constructor
+Expr::Expr(Expr &&other) noexcept : type{other.type}, value{std::move(other.value)} {}
+
+// Copy assignment
+Expr &Expr::operator=(const Expr &other) {
+  if (this == &other) {
+    return *this;
   }
+
+  type  = other.type;
+  value = other.value;
+
+  return *this;
 }
 
-std::string AstPrinter::parenthesize(const std::string &name, std::vector<Expr> exprs) {
-  std::stringstream ss{};
-  ss << '(' << name;
-  for (auto &expr : exprs) {
-    ss << ' ' << print(expr);
+// Move assignment
+Expr &Expr::operator=(Expr &&other) noexcept {
+  if (this == &other) {
+    return *this;
   }
-  ss << ')';
 
-  return ss.str();
+  type  = std::move(other.type);
+  value = std::move(other.value);
+
+  return *this;
 }

cclox_src/parser/expr.hh

@@ -3,60 +3,94 @@
 
 #include "../tokenizer.hh"
 #include <memory>
-#include <string>
 #include <variant>
 
 struct Expr;
-
-using ExprPtr = std::shared_ptr<Expr>;
-
-struct Binary {
-  Binary(ExprPtr left, Token op, ExprPtr right) : left{left}, op{op}, right{right} {};
-
-  ExprPtr left;
-  Token op;
-  ExprPtr right;
-};
-
-struct Grouping {
-  Grouping(ExprPtr expr) : expression{expr} {};
-
-  ExprPtr expression;
-};
-
-struct Literal {
-  Literal(Object value) : value{value} {};
-
-  Object value;
-};
-
-struct Unary {
-  Unary(Token op, ExprPtr right) : op{op}, right{right} {};
-
-  Token op;
-  ExprPtr right;
-};
+struct _Binary;
+struct _Grouping;
+struct _Literal;
+struct _Unary;
+struct _Variable;
+struct _Assign;
 
 enum class ExprType {
   BINARY,
   GROUPING,
   LITERAL,
   UNARY,
+  VARIABLE,
+  ASSIGN,
 };
 
-using Expression = std::variant<Binary, Grouping, Literal, Unary>;
+using ExprVariant = std::variant<
+  std::shared_ptr<_Binary>,
+  std::shared_ptr<_Grouping>,
+  std::shared_ptr<_Literal>,
+  std::shared_ptr<_Unary>,
+  std::shared_ptr<_Variable>,
+  std::shared_ptr<_Assign>
+>;
+
+#define Binary(LEFT, OP, RIGHT) (Expr{ExprType::BINARY, std::make_shared<_Binary>(LEFT, OP, RIGHT)})
+#define Grouping(EXPR) (Expr{ExprType::GROUPING, std::make_shared<_Grouping>(EXPR)})
+#define Literal(VALUE) (Expr{ExprType::LITERAL, std::make_shared<_Literal>(VALUE)})
+#define Unary(OP, RIGHT) (Expr{ExprType::UNARY, std::make_shared<_Unary>(OP, RIGHT)})
+#define Variable(NAME) (Expr{ExprType::VARIABLE, std::make_shared<_Variable>(NAME)})
+#define Assign(NAME, VALUE) (Expr{ExprType::ASSIGN, std::make_shared<_Assign>(NAME, VALUE)})
 
 struct Expr {
-  Expr(ExprType type, Expression value) : type{type}, value{value} {}
+  Expr(ExprType type, ExprVariant value);
+
+  // Copy constructor
+  Expr(const Expr &other);
+
+  // Move constructor
+  Expr(Expr &&other) noexcept;
+
+  // Copy assignment
+  Expr &operator=(const Expr &other);
+
+  // Move assignment
+  Expr &operator=(Expr &&other) noexcept;
+
+  ~Expr() = default;
+
   ExprType type;
-  Expression value;
+  ExprVariant value;
 };
 
-class AstPrinter {
-public:
-  std::string print(const Expr &expr);
-private:
-  std::string parenthesize(const std::string &name, std::vector<Expr> exprs);
+struct _Binary {
+  _Binary(const Expr &left, Token op, const Expr &right) : left{left}, op{op}, right{right} {}
+  Expr left;
+  Token op;
+  Expr right;
+};
+
+struct _Grouping {
+  _Grouping(const Expr &expr) : expr{expr} {}
+  Expr expr;
+};
+
+struct _Literal {
+  _Literal(Object value) : value{value} {}
+  Object value;
+};
+
+struct _Unary {
+  _Unary(Token op, const Expr &right) : op{op}, right{right} {}
+  Token op;
+  Expr right;
+};
+
+struct _Variable {
+  _Variable(Token name) : name{name} {}
+  Token name;
+};
+
+struct _Assign {
+  _Assign(Token name, const Expr &value) : name{name}, value{value} {}
+  Token name;
+  Expr value;
 };
 
 #endif

cclox_src/parser/parser.cc

@@ -0,0 +1,272 @@
+#include "parser.hh"
+#include "expr.hh"
+#include "stmt.hh"
+#include "../error_handler.hh"
+#include "../tokenizer.hh"
+#include <cassert>
+
+extern ErrorHandler error_handler;
+
+std::vector<Stmt> Parser::parse() {
+  std::vector<Stmt> statements{};
+  while (!is_at_end()) {
+    statements.push_back(declaration());
+  }
+
+  return statements;
+}
+
+Stmt Parser::declaration() {
+  try {
+    if (match({TokenType::VAR})) {
+      return var_declaration();
+    }
+
+    return statement();
+  } catch (ParseException e) {
+    synchronize();
+    return Expression(Literal(Object{}));
+  }
+}
+
+Stmt Parser::var_declaration() {
+  Token name       = consume(TokenType::IDENTIFIER, "Expect variable name.");
+  Expr initializer = Literal(Object{});
+
+  if (match({TokenType::EQUAL})) {
+    initializer = expression();
+  }
+
+  consume(TokenType::SEMICOLON, "Expect ';' after variable declaration");
+  return Var(name, initializer);
+}
+
+Stmt Parser::statement() {
+  if (match({TokenType::PRINT})) {
+    return print_statement();
+  }
+
+  if (match({TokenType::LEFT_BRACE})) {
+    return Block(block_statement());
+  }
+
+  return expression_statement();
+}
+
+std::vector<Stmt> Parser::block_statement() {
+  std::vector<Stmt> statements{};
+
+  while (!check(TokenType::RIGHT_BRACE) && !is_at_end()) {
+    statements.push_back(declaration());
+  }
+
+  consume(TokenType::RIGHT_BRACE, "Expect '}' after block.");
+  return statements;
+}
+
+Stmt Parser::print_statement() {
+  Expr value{expression()};
+  consume(TokenType::SEMICOLON, "Expect ';' after value.");
+  return Print(value);
+}
+
+Stmt Parser::expression_statement() {
+  Expr value{expression()};
+  consume(TokenType::SEMICOLON, "Expect ';' after value.");
+  return Expression(value);
+}
+
+Expr Parser::expression() {
+  return assignment();
+}
+
+Expr Parser::assignment() {
+  Expr expr = equality();
+
+  if (match({TokenType::EQUAL})) {
+    Token equals = previous();
+    Expr value   = assignment();
+
+    if (expr.type == ExprType::VARIABLE) {
+      std::shared_ptr<_Variable> ptr = std::get<std::shared_ptr<_Variable>>(expr.value);
+      assert(ptr != nullptr);
+      Token name = ptr->name;
+      return Assign(name, value);
+    }
+
+    error_handler.error(equals, "Invalid assignment target.");
+  }
+
+  return expr;
+}
+
+Expr Parser::equality() {
+  Expr expr = comparison();
+
+  while (match({TokenType::BANG_EQUAL, TokenType::EQUAL_EQUAL})) {
+    Token op   = previous();
+    Expr right = comparison();
+    expr       = Binary(expr, op, right);
+  }
+
+  return expr;
+}
+
+Expr Parser::comparison() {
+  Expr expr = term();
+
+  while (match({TokenType::GREATER, TokenType::GREATER_EQUAL, TokenType::LESS, TokenType::LESS_EQUAL})) {
+    Token op   = previous();
+    Expr right = term();
+    expr       = Binary(expr, op, right);
+  }
+
+  return expr;
+}
+
+Expr Parser::term() {
+  Expr expr = factor();
+
+  while (match({TokenType::MINUS, TokenType::PLUS})) {
+    Token op = previous();
+    Expr right = factor();
+    expr = Binary(expr, op, right);
+  }
+
+  return expr;
+}
+
+Expr Parser::factor() {
+  Expr expr = unary();
+
+  while (match({TokenType::SLASH, TokenType::STAR})) {
+    Token op   = previous();
+    Expr right = unary();
+    expr       = Binary(expr, op, right);
+  }
+
+  return expr;
+}
+
+Expr Parser::unary() {
+  if (match({TokenType::BANG, TokenType::MINUS})) {
+    Token op   = previous();
+    Expr right = unary();
+
+    return Unary(op, right);
+  }
+
+  return primary();
+}
+
+Expr Parser::primary() {
+  if (match({TokenType::FALSE})) {
+    return Literal(false);
+  }
+
+  if (match({TokenType::TRUE})) {
+    return Literal(true);
+  }
+
+  if (match({TokenType::NIL})) {
+    return Literal(Object{});
+  }
+
+  if (match({TokenType::NUMBER, TokenType::STRING})) {
+    return Literal(previous().literal);
+  }
+
+  if (match({TokenType::IDENTIFIER})) {
+    return Variable(previous());
+  }
+
+  if (match({TokenType::LEFT_PAREN})) {
+    Expr expr = expression();
+    consume(TokenType::RIGHT_PAREN, "Expect ')' after expression.");
+    return Grouping(expr);
+  }
+
+  throw error(peek(), "Expect expression.");
+}
+
+Token Parser::advance() {
+  if (!is_at_end()) {
+    ++current;
+  }
+
+  return previous();
+}
+
+Token Parser::peek() {
+  return tokens.at(current);
+}
+
+Token Parser::previous() {
+  return tokens.at(current - 1);
+}
+
+Token Parser::consume(TokenType type, std::string &&message) {
+  if (check(type)) {
+    return advance();
+  }
+
+  throw error(peek(), message);
+}
+
+bool Parser::match(std::vector<TokenType> types) {
+  for (const auto &type : types) {
+    if (check(type)) {
+      advance();
+      return true;
+    }
+  }
+
+  return false;
+}
+
+bool Parser::check(TokenType type) {
+  if (is_at_end()) {
+    return false;
+  }
+
+  return peek().type == type;
+}
+
+bool Parser::is_at_end() {
+  return peek().type == TokenType::EOFILE;
+}
+
+ParseException Parser::error(Token token, std::string &message) {
+  error_handler.error(token, message);
+  return ParseException{};
+}
+
+ParseException Parser::error(Token token, std::string &&message) {
+  return error(token, message);
+}
+
+void Parser::synchronize() {
+  advance();
+
+  while (!is_at_end()) {
+    if (previous().type == TokenType::SEMICOLON) {
+      return;
+    }
+
+    switch (peek().type) {
+      case TokenType::CLASS:
+      case TokenType::FUN:
+      case TokenType::VAR:
+      case TokenType::FOR:
+      case TokenType::IF:
+      case TokenType::WHILE:
+      case TokenType::PRINT:
+      case TokenType::RETURN:
+        return;
+      default:
+        break;
+    }
+
+    advance();
+  }
+}

cclox_src/parser/parser.hh

@@ -0,0 +1,54 @@
+#ifndef PARSER_HH
+#define PARSER_HH
+
+#include "expr.hh"
+#include "stmt.hh"
+#include "../tokenizer.hh"
+#include <cstddef>
+#include <exception>
+#include <vector>
+
+struct ParseException : public std::exception {
+  ParseException() : message{""} {}
+  ParseException(const std::string& message) : message{message} {}
+  const char* what() const noexcept override {
+      return message.c_str();
+  }
+
+private:
+  std::string message;
+};
+
+struct Parser {
+  Parser(std::vector<Token> tokens) : tokens{tokens} {}
+  std::vector<Stmt> parse();
+  Stmt declaration();
+  Stmt var_declaration();
+  Stmt statement();
+  std::vector<Stmt> block_statement();
+  Stmt print_statement();
+  Stmt expression_statement();
+  Expr expression();
+  Expr assignment();
+  Expr equality();
+  Expr comparison();
+  Expr term();
+  Expr factor();
+  Expr unary();
+  Expr primary();
+  Token advance();
+  Token peek();
+  Token previous();
+  Token consume(TokenType type, std::string &&message);
+  bool match(std::vector<TokenType> types);
+  bool check(TokenType type);
+  bool is_at_end();
+  ParseException error(Token token, std::string &message);
+  ParseException error(Token token, std::string &&message);
+  void synchronize();
+
+  std::vector<Token> tokens;
+  size_t current = 0;
+};
+
+#endif

cclox_src/parser/stmt.cc

@@ -0,0 +1,35 @@
+#include "stmt.hh"
+#include <cassert>
+#include <utility>
+
+Stmt::Stmt(StmtType type, StmtVariant value) : type{type}, value{value} {}
+
+// Copy constructor
+Stmt::Stmt(const Stmt &other) : type{other.type}, value{other.value} {}
+
+// Move constructor
+Stmt::Stmt(Stmt &&other) noexcept : type{other.type}, value{std::move(other.value)} {}
+
+// Copy assignment
+Stmt &Stmt::operator=(const Stmt &other) {
+  if (this == &other) {
+    return *this;
+  }
+
+  type  = other.type;
+  value = other.value;
+
+  return *this;
+}
+
+// Move assignment
+Stmt &Stmt::operator=(Stmt &&other) noexcept {
+  if (this == &other) {
+    return *this;
+  }
+
+  type  = std::move(other.type);
+  value = std::move(other.value);
+
+  return *this;
+}

cclox_src/parser/stmt.hh

@@ -0,0 +1,76 @@
+#ifndef STMT_HH
+#define STMT_HH
+
+#include "expr.hh"
+#include <memory>
+#include <variant>
+#include <vector>
+
+struct Stmt;
+struct _Expression;
+struct _Print;
+struct _Var;
+struct _Block;
+
+enum class StmtType {
+  EXPRESSION,
+  PRINT,
+  VAR,
+  BLOCK,
+};
+
+using StmtVariant = std::variant<
+  std::shared_ptr<_Expression>,
+  std::shared_ptr<_Print>,
+  std::shared_ptr<_Var>,
+  std::shared_ptr<_Block>
+>;
+
+#define Expression(EXPR) (Stmt{StmtType::EXPRESSION, std::make_shared<_Expression>(EXPR)})
+#define Print(EXPR) (Stmt{StmtType::PRINT, std::make_shared<_Print>(EXPR)})
+#define Var(NAME, EXPR) (Stmt{StmtType::VAR, std::make_shared<_Var>(NAME, EXPR)})
+#define Block(STATEMENTS) (Stmt{StmtType::BLOCK, std::make_shared<_Block>(STATEMENTS)})
+
+struct Stmt {
+  Stmt(StmtType type, StmtVariant value);
+
+  // Copy constructor
+  Stmt(const Stmt &other);
+
+  // Move constructor
+  Stmt(Stmt &&other) noexcept;
+
+  // Copy assignment
+  Stmt &operator=(const Stmt &other);
+
+  // Move assignment
+  Stmt &operator=(Stmt &&other) noexcept;
+
+  ~Stmt() = default;
+
+  StmtType type;
+  StmtVariant value;
+};
+
+struct _Expression {
+  _Expression(const Expr &expr) : expr{expr} {}
+  Expr expr;
+};
+
+struct _Print {
+  _Print(const Expr &expr) : expr{expr} {}
+  Expr expr;
+};
+
+struct _Var {
+  _Var(const Token &name, const Expr &expr) : name{name}, expr{expr} {}
+  Token name;
+  Expr expr;
+};
+
+struct _Block {
+  _Block(const std::vector<Stmt> &statements) : statements{statements} {}
+  std::vector<Stmt> statements;
+};
+
+#endif

cclox_src/scanner/object.cc

@@ -1,11 +1,68 @@
 #include "object.hh"
+#include <cstddef>
 #include <string>
 
+std::string Object::to_string() const {
+  switch (type) {
+    case ObjectType::NIL:
+      return "nil";
+    case ObjectType::BOOL: {
+      bool val = std::get<bool>(value);
+      return (val ? "true" : "false");
+    }
+    case ObjectType::IDENTIFIER:
+    case ObjectType::STRING_LIT: {
+      std::string val = std::get<std::string>(value);
+      return val;
+    }
+    case ObjectType::NUMBER: {
+      double val = std::get<double>(value);
+      std::string output{std::to_string(val)};
+      if (val == ((int)val)) {
+        size_t decimal_index{output.find(".")};
+        output = output.substr(0, decimal_index);
+      }
+      return output;
+    }
+  }
+}
+
+bool Object::operator==(const Object &other) {
+  if (type != other.type) {
+    return false;
+  }
+
+  switch (type) {
+    case ObjectType::NIL: return true;
+    case ObjectType::BOOL: {
+      bool left  = std::get<bool>(value);
+      bool right = std::get<bool>(other.value);
+
+      return left == right;
+    }
+    case ObjectType::IDENTIFIER:
+    case ObjectType::STRING_LIT: {
+      std::string left  = std::get<std::string>(value);
+      std::string right = std::get<std::string>(other.value);
+
+      return left == right;
+    }
+    case ObjectType::NUMBER: {
+      double left  = std::get<double>(value);
+      double right = std::get<double>(other.value);
+
+      return left == right;
+    }
+  }
+}
+
 std::ostream &operator<<(std::ostream &os, const ObjectType &type) {
   switch (type) {
     case ObjectType::NIL:
       os << "ObjectType::NIL";
       break;
+    case ObjectType::BOOL:
+      os << "ObjectType::BOOL";
     case ObjectType::IDENTIFIER:
       os << "ObjectType::IDENTIFIER";
       break;
@@ -21,21 +78,10 @@ std::ostream &operator<<(std::ostream &os, const ObjectType &type) {
 }
 
 std::ostream &operator<<(std::ostream &os, const Object &obj) {
-  os << "Object(" << obj.type;
-
-  switch (obj.type) {
-    case ObjectType::NIL:
-      break;
-    case ObjectType::IDENTIFIER:
-    case ObjectType::STRING_LIT:
-      os << ", " << std::get<std::string>(obj.value);
-      break;
-    case ObjectType::NUMBER:
-      os << ", " << std::get<double>(obj.value);
-      break;
-  }
-
-  os << ')';
-
+  os << obj.to_string();
   return os;
 }
+
+bool Object::operator!=(const Object &other) {
+  return !operator==(other);
+}

cclox_src/scanner/object.hh

@@ -12,6 +12,7 @@ enum class StringObjectType : uint8_t {
 
 enum class ObjectType : uint8_t {
   NIL,
+  BOOL,
   IDENTIFIER,
   STRING_LIT,
   NUMBER,
@@ -19,6 +20,7 @@ enum class ObjectType : uint8_t {
 
 struct Object {
   Object() : type{ObjectType::NIL}, value{std::monostate{}} {};
+  Object(bool value) : type{ObjectType::BOOL}, value{value} {};
   Object(double number) : type{ObjectType::NUMBER}, value{number} {};
   Object(StringObjectType string_type, std::string value)
     : type{
@@ -27,9 +29,12 @@ struct Object {
         ObjectType::STRING_LIT
       },
       value{std::move(value)} {};
+  std::string to_string() const;
+  bool operator==(const Object &other);
+  bool operator!=(const Object &other);
 
   ObjectType type;
-  std::variant<std::monostate, std::string, double> value;
+  std::variant<std::monostate, std::string, double, bool> value;
 };
 
 std::ostream &operator<<(std::ostream &os, const ObjectType &type);