lox.java

package SLox;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.nio.file.Paths;
import java.util.List;

public class lox {
  private static final Interpreter interpreter = new Interpreter();

  static boolean hadError = false;
    static boolean hadRuntimeError = false;

    
  public static void main(String[] args) throws IOException {
    if (args.length > 1) {
      System.out.println("Usage: jlox [script]");
      System.exit(64); 
    } else if (args.length == 1) {
      runFile(args[0]);
    } else {
      runPrompt();
    }

  }
  private static void runFile(String path) throws IOException {
    byte[] bytes = Files.readAllBytes(Paths.get(path));
    run(new String(bytes, Charset.defaultCharset()),false);

    if (hadError) System.exit(65);
    if (hadRuntimeError) System.exit(70);

  }
    private static void runPrompt() throws IOException {
        InputStreamReader input = new InputStreamReader(System.in);
        BufferedReader reader = new BufferedReader(input);
        for (;;) { 
          System.out.print("> ");
          String line = reader.readLine();
          if (line == null) break;
          run(line, true);
          hadError = false;
        }

        // Indicate an error in the exit code.
   
    }
  private static void run(String source, boolean isR) {
    Scanner scanner = new Scanner(source);
    List<Token> tokens = scanner.scanTokens();
    Parser parser = new Parser(tokens);
    List<Stmt> statements = parser.parse();
    // Stop if there was a syntax error.
    if (hadError) return;
    Resolver resolver = new Resolver(interpreter);
    resolver.resolve(statements);
    checkVisitedVariables(resolver);
    // Stop if there was a resolution error.
    if (hadError) return;
    interpreter.interpret(statements,isR);

    //System.out.println(new AstPrinter().print(expressions));
}
  private static void checkVisitedVariables(Resolver resolver){

    if(!resolver.visited.isEmpty())
      lox.error(resolver.visited.get(0),
              "Variable is defined but never used.");
  }

  private static void report(int line, String where,
  String message) {
  System.err.println(
  "[line " + line + "] Error" + where + ": " + message);
  hadError = true;
  }
  static void error(int line, String message) {
  report(line, "", message);
  }
  static void error(Token token, String message) {
  if (token.type == TokenType.EOF) {
  report(token.line, " at end", message);
  } else {
  report(token.line, " at '" + token.lexeme + "'", message);
  }
  }

  static void runtimeError(RuntimeError error) {
    System.err.println(error.getMessage() +
            "\n[line " + error.token.line + "]");
    hadRuntimeError = true;
  }
}