initial commit, template added

MicroJava Compiler/src/ssw/mj/impl/Parser.java

@@ -0,0 +1,144 @@
+package ssw.mj.impl;
+
+import ssw.mj.Errors;
+import ssw.mj.Errors.Message;
+import ssw.mj.scanner.Token;
+
+import static ssw.mj.Errors.Message.TOKEN_EXPECTED;
+import static ssw.mj.scanner.Token.Kind.eof;
+import static ssw.mj.scanner.Token.Kind.none;
+
+public final class Parser {
+
+  /**
+   * Maximum number of global variables per program
+   */
+  private static final int MAX_GLOBALS = 32767;
+
+  /**
+   * Maximum number of fields per class
+   */
+  private static final int MAX_FIELDS = 32767;
+
+  /**
+   * Maximum number of local variables per method
+   */
+  private static final int MAX_LOCALS = 127;
+
+  /**
+   * Last recognized token;
+   */
+  private Token t;
+
+  /**
+   * Lookahead token (not recognized).)
+   */
+  private Token la;
+
+  /**
+   * Shortcut to kind attribute of lookahead token (la).
+   */
+  private Token.Kind sym;
+
+  /**
+   * According scanner
+   */
+  public final Scanner scanner;
+
+  /**
+   * According code buffer
+   */
+  public final Code code;
+
+  /**
+   * According symbol table
+   */
+  public final Tab tab;
+
+  public Parser(Scanner scanner) {
+    this.scanner = scanner;
+    tab = new Tab(this);
+    code = new Code(this);
+    // Pseudo token to avoid crash when 1st symbol has scanner error.
+    la = new Token(none, 1, 1);
+  }
+
+
+  /**
+   * Reads ahead one symbol.
+   */
+  private void scan() {
+    t = la;
+    la = scanner.next();
+    sym = la.kind;
+  }
+
+  /**
+   * Verifies symbol and reads ahead.
+   */
+  private void check(Token.Kind expected) {
+    if (sym == expected) {
+      scan();
+    } else {
+      error(TOKEN_EXPECTED, expected);
+    }
+  }
+
+  /**
+   * Adds error message to the list of errors.
+   */
+  public void error(Message msg, Object... msgParams) {
+    // TODO Exercise UE-P-3: Replace panic mode with error recovery (i.e., keep track of error distance)
+    // TODO Exercise UE-P-3: Hint: Replacing panic mode also affects scan() method
+    scanner.errors.error(la.line, la.col, msg, msgParams);
+    throw new Errors.PanicMode();
+  }
+
+  /**
+   * Starts the analysis.
+   */
+  public void parse() {
+    scan(); // scan first symbol, initializes look-ahead
+    Program(); // start analysis
+    check(eof);
+  }
+
+
+  // ===============================================
+  // TODO Exercise UE-P-2: Implementation of parser
+  // TODO Exercise UE-P-3: Error recovery methods
+  // TODO Exercise UE-P-4: Symbol table handling
+  // TODO Exercise UE-P-5-6: Code generation
+  // ===============================================
+
+  // TODO Exercise UE-P-3: Error distance
+
+  // TODO Exercise UE-P-2 + Exercise 3: Sets to handle certain first, follow, and recover sets
+
+  static {
+    // Initialize first and follow sets.
+  }
+
+  // ---------------------------------
+
+  // TODO Exercise UE-P-2: One top-down parsing method per production
+
+  /**
+   * Program = <br>
+   * "program" ident <br>
+   * { ConstDecl | VarDecl | ClassDecl } <br>
+   * "{" { MethodDecl } "}" .
+   */
+  private void Program() {
+    // TODO Exercise UE-P-2
+  }
+
+  // ...
+
+  // ------------------------------------
+
+  // TODO Exercise UE-P-3: Error recovery methods: recoverDecl, recoverMethodDecl and recoverStat (+ TODO Exercise UE-P-5: Check idents for Type kind)
+
+  // ====================================
+  // ====================================
+}