Start implementing the parser

cclox_src/main.cc

@@ -1,17 +1,29 @@
 #include "interpreter.hh"
 #include "error_handler.hh"
+#include "parser.hh"
 #include <iostream>
 #include <sysexits.h>
 
 ErrorHandler error_handler{};
 
 int main(int argc, char *argv[]) {
-  if (argc > 2) {
-    std::cout << "Usage: cclox [script]\n";
-    exit(EX_USAGE);
-  }
+  (void)argc;
+  (void)argv;
+  // if (argc > 2) {
+  //   std::cout << "Usage: cclox [script]\n";
+  //   exit(EX_USAGE);
+  // }
+  //
+  // run_interpreter(argc, argv);
 
-  run_interpreter(argc, argv);
+  Unary left {Token{TokenType::MINUS, "-", Object{}, 1}, Literal{123}};
+  Token op{TokenType::STAR, "*", Object{}, 1};
+  Grouping right{Literal{45.67}};
+
+  Binary expr {left, op, right};
+
+  AstPrinter printer{};
+  std::cout << printer.print(expr) << '\n';
 
   return 0;
 }

cclox_src/parser.cc

@@ -0,0 +1,6 @@
+#ifndef PARSER_CC
+#define PARSER_CC
+
+#include "parser/expr.cc"
+
+#endif

cclox_src/parser.hh

@@ -0,0 +1,6 @@
+#ifndef PARSER_HH
+#define PARSER_HH
+
+#include "parser/expr.hh"
+
+#endif

cclox_src/parser/expr.cc

@@ -0,0 +1,51 @@
+#include "expr.hh"
+#include "../tokenizer.hh"
+#include <string>
+#include <type_traits>
+#include <variant>
+#include <vector>
+#include <sstream>
+
+std::string AstPrinter::print(const Expression &expr) {
+  return std::visit([this](auto &&node) -> std::string {
+    using T = std::decay_t<decltype(node)>;
+
+    if constexpr(std::is_same_v<T, Binary>) {
+      return parenthesize(node.op.lexeme, {node.left, node.right});
+    } else if constexpr(std::is_same_v<T, Grouping>) {
+      return parenthesize("group", {node.expression});
+    } else if constexpr(std::is_same_v<T, Literal>) {
+      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);
+        }
+      }
+    } else if constexpr(std::is_same_v<T, Unary>) {
+      return parenthesize(node.op.lexeme, {node.right});
+    }
+
+    return "";
+  }, expr);
+}
+
+std::string AstPrinter::parenthesize(const std::string &name, std::vector<Expression> exprs) {
+  std::stringstream ss{};
+  ss << '(' << name;
+  for (auto &expr : exprs) {
+    std::string value = std::visit([this](auto &&node) -> std::string {
+      return print(node);
+    }, expr);
+    ss << ' ' << value;
+  }
+  ss << ')';
+
+  return ss.str();
+}

cclox_src/parser/expr.hh

@@ -0,0 +1,46 @@
+#ifndef EXPR_HH
+#define EXPR_HH
+
+#include "../tokenizer.hh"
+#include <string>
+#include <variant>
+
+struct Expr {};
+
+struct Binary : public Expr {
+  Binary(Expr left, Token op, Expr right) : left{left}, op{op}, right{right} {};
+
+  Expr left;
+  Token op;
+  Expr right;
+};
+
+struct Grouping : public Expr {
+  Grouping(Expr expr) : expression{expr} {};
+
+  Expr expression;
+};
+
+struct Literal : public Expr {
+  Literal(Object value) : value{value} {};
+
+  Object value;
+};
+
+struct Unary : public Expr {
+  Unary(Token op, Expr right) : op{op}, right{right} {};
+
+  Token op;
+  Expr right;
+};
+
+using Expression = std::variant<Expr, Binary, Grouping, Literal, Unary>;
+
+class AstPrinter {
+public:
+  std::string print(const Expression &expr);
+private:
+  std::string parenthesize(const std::string &name, std::vector<Expression> exprs);
+};
+
+#endif