add Parser

src/Parser.cpp

@@ -0,0 +1,129 @@
+#include "Parser.hpp"
+
+Parser::Parser(Lexer lexer) : lexer(lexer), curToken(Token()), peekToken(Token())
+{
+  nextToken();
+  nextToken();
+}
+bool Parser::checkToken(TokenType kind)
+{
+  return kind = (this->curToken).get_kind();
+}
+bool Parser::checkPeek(TokenType kind)
+{
+  return kind = (this->peekToken).get_kind();
+}
+void Parser::match(TokenType kind)
+{
+  if (!checkToken(kind))
+  {
+    abort("Expected " + token_name(kind) + ", got " + token_name((this->curToken).get_kind()));
+  }
+  nextToken();
+}
+
+Token Parser::nextToken()
+{
+  this->curToken = this->peekToken;
+  this->peekToken = (this->lexer).getToken();
+}
+void Parser::abort(std::string message)
+{
+  std::cout << "Error: " << message << std::endl;
+  exit(1);
+}
+
+void Parser::program()
+{
+  while (checkToken(TokenType::NEWLINE)){
+    nextToken();
+  }
+  while (!checkToken(TokenType::END_OF_FILE))
+  {
+    statement();
+  }
+}
+
+void Parser::statement()
+{
+  // "PRINT" (expression | string)
+  if (checkToken(TokenType::PRINT))
+  {
+    nextToken();
+
+    if (checkToken(TokenType::STRING))
+    {
+      nextToken();
+    }
+    else
+    {
+      expression();
+    }
+  }
+
+  // "IF" comparison "THEN" nl {statement} "ENDIF"
+  else if (checkToken(TokenType::IF))
+  {
+    nextToken();
+    comparison();
+    match(TokenType::THEN);
+    nl();
+    while (!checkToken(TokenType::ENDIF))
+    {
+      statement();
+    }
+    match(TokenType::ENDIF);
+  }
+
+  // "WHILE" comparison "REPEAT" nl {statement nl} "ENDWHILE"
+  else if (checkToken(TokenType::WHILE))
+  {
+    nextToken();
+    comparison();
+    match(TokenType::REPEAT);
+    nl();
+    while (!checkToken(TokenType::ENDWHILE))
+    {
+      statement();
+    }
+    match(TokenType::ENDWHILE);
+  }
+
+  // "LABEL" ident
+  else if (checkToken(TokenType::LABEL)){
+    nextToken();
+    ident();
+  }
+
+  // "GOTO" ident
+  else if (checkToken(TokenType::GOTO)){
+    nextToken();
+    ident();
+  }
+  // "LET" ident "=" expression
+  else if (checkToken(TokenType::LET)){
+    nextToken();
+    ident();
+    match(TokenType::EQ);
+    expression();
+  }
+  // "INPUT" ident
+  if (checkToken(TokenType::INPUT)){
+    nextToken();
+    ident();
+  }
+
+  else{
+    abort("Invalid statement at "+ (this->curToken).get_text() + "(" + token_name((this->curToken).get_kind()) + ")");
+  }
+  nl();
+}
+
+void Parser::nl()
+{
+  match(TokenType::NEWLINE);
+  while (checkToken(TokenType::NEWLINE))
+  {
+    nextToken();
+  }
+}

src/Parser.hpp

@@ -0,0 +1,22 @@
+#include "Lexer.hpp"
+
+class Parser {
+  Lexer lexer;
+  Token curToken;
+  Token peekToken;
+
+  public:
+  Parser(Lexer lexer);
+  bool checkToken(TokenType kind);
+  bool checkPeek(TokenType kind);
+  void match(TokenType kind);
+  Token nextToken();
+  void abort(std::string message);
+
+  void program();
+  void statement();
+  void expression();
+  void comparison();
+  void ident();
+  void nl();
+};