Example #1
0
  /**
   * Parse an expression
   *
   * @param token the initial token.
   * @return the root of the generated parse subtree.
   * @throws Exception if an error occurred.
   */
  private ICodeNode parseExpression(Token token) throws Exception {
    // Parse a simple expression and make the root of its tree
    // the root node.
    ICodeNode rootNode = parseSimpleExpression(token);
    TypeSpec resultType = rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;

    token = currentToken();
    TokenType tokenType = token.getType();

    // Look for a relational operator.
    if (REL_OPS.contains(tokenType)) {
      // Create a new operator node and adopt the current tree as its first child
      ICodeNodeType nodeType = REL_OPS_MAP.get(tokenType);
      ICodeNode opNode = ICodeFactory.createICodeNode(nodeType);
      opNode.addChild(rootNode);

      token = nextToken(); // consume the operator

      // Parse the second simple expression.
      // The operator node adopts the simple expression's tree as its second child.
      ICodeNode simExprNode = parseSimpleExpression(token);
      opNode.addChild(simExprNode);

      // The operator node becomes the new root node.
      rootNode = opNode;

      // Type check: The operands must be comparison compatible.
      TypeSpec simExprType =
          simExprNode != null ? simExprNode.getTypeSpec() : Predefined.undefinedType;
      if (TypeChecker.areComparisionCompatible(resultType, simExprType))
        resultType = Predefined.booleanType;
      else {
        errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
        resultType = Predefined.undefinedType;
      }
    }

    if (rootNode != null) rootNode.setTypeSpec(resultType);
    return rootNode;
  }
Example #2
0
  /**
   * Parse a term.
   *
   * @param token the initial token.
   * @return the root of the generated parse subtree.
   * @throws Exception if an error occurred.
   */
  private ICodeNode parseTerm(Token token) throws Exception {
    // Parse a factor and makes its node the root node.
    ICodeNode rootNode = parseFactor(token);
    TypeSpec resultType = rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;

    token = currentToken();
    TokenType tokenType = token.getType();

    // Loop over multiplicative operators.
    while (MULT_OPS.contains(tokenType)) {
      TokenType operator = tokenType;

      // Create a new operator node and adopt the current tree as its first child.
      ICodeNodeType nodeType = MULT_OPS_OPS_MAP.get(operator);
      ICodeNode opNode = ICodeFactory.createICodeNode(nodeType);
      opNode.addChild(rootNode);

      token = nextToken(); // consume the operator

      // Parse another factor.
      // The operator node adopts the term's tree as its secomd child.
      ICodeNode factorNode = parseFactor(token);
      opNode.addChild(factorNode);
      TypeSpec factorType =
          factorNode != null ? factorNode.getTypeSpec() : Predefined.undefinedType;
      // The operator node becomes the new root node.
      rootNode = opNode;

      // Determine the result type.
      switch ((PascalTokenType) operator) {
        case STAR:
          {
            // Both operands integer ==> integer result.
            if (TypeChecker.areBothInteger(resultType, factorType)) {
              resultType = Predefined.integerType;
            }

            // Both real operands or one real and one integer operand
            // ==> real result.
            else if (TypeChecker.isAtLeastOneReal(resultType, factorType)) {
              resultType = Predefined.realType;
            } else {
              errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            }

            break;
          }

        case SLASH:
          {
            // All integer and real operand combinations
            // ==> real result.
            if (TypeChecker.areBothInteger(resultType, factorType)
                || TypeChecker.isAtLeastOneReal(resultType, factorType)) {
              resultType = Predefined.realType;
            } else {
              errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            }

            break;
          }

        case DIV:
        case MOD:
          {
            // Both operands integer ==> integer result.
            if (TypeChecker.areBothInteger(resultType, factorType)) {
              resultType = Predefined.integerType;
            } else {
              errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            }

            break;
          }

        case AND:
          {
            // Both operands boolean ==> boolean result.
            if (TypeChecker.areBothBoolean(resultType, factorType)) {
              resultType = Predefined.booleanType;
            } else {
              errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            }

            break;
          }
      }

      // The operator node becomes the new root node.
      rootNode.setTypeSpec(resultType);

      token = currentToken();
      tokenType = token.getType();
    }
    return rootNode;
  }
Example #3
0
  /**
   * Parse a factor.
   *
   * @param token the initial token.
   * @return the root of the generated parse subtree.
   * @throws Exception if an error occurred.
   */
  private ICodeNode parseFactor(Token token) throws Exception {
    TokenType tokenType = token.getType();
    ICodeNode rootNode = null;

    switch ((PascalTokenType) tokenType) {
      case IDENTIFIER:
        {
          return parseIdentifier(token);
        }

      case INTEGER:
        {
          // Create an INTEGER_CONSTANT node as the root node
          rootNode = ICodeFactory.createICodeNode(INTEGER_CONSTANT);
          rootNode.setAttribute(VALUE, token.getValue());

          token = nextToken(); // consume the number
          rootNode.setTypeSpec(Predefined.integerType);
          break;
        }

      case REAL:
        {
          // Create an REAL_CONSTANT node as the root node.
          rootNode = ICodeFactory.createICodeNode(REAL_CONSTANT);
          rootNode.setAttribute(VALUE, token.getValue());

          token = nextToken(); // consume the number

          rootNode.setTypeSpec(Predefined.realType);
          break;
        }

      case STRING:
        {
          String value = (String) token.getValue();

          // Create a STRING_CONSTANT node as the root node.
          rootNode = ICodeFactory.createICodeNode(STRING_CONSTANT);
          rootNode.setAttribute(VALUE, value);

          TypeSpec resultType =
              value.length() == 1 ? Predefined.charType : TypeFactory.createStringType(value);

          token = nextToken(); // consume the string
          rootNode.setTypeSpec(resultType);
          break;
        }

      case NOT:
        {
          token = nextToken(); // consume the NOT

          // Create a NOT node as the root node.
          rootNode = ICodeFactory.createICodeNode(ICodeNodeTypeImpl.NOT);

          // Parse the factor. The NOT node adopts the factor node as its child.
          ICodeNode factorNode = parseFactor(token);
          rootNode.addChild(factorNode);

          // Type check: the factor must be boolean.
          TypeSpec factorType =
              factorNode != null ? factorNode.getTypeSpec() : Predefined.undefinedType;
          if (!TypeChecker.isBoolean(factorType))
            errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
          rootNode.setTypeSpec(Predefined.booleanType);
          break;
        }

      case LEFT_PAREN:
        {
          token = nextToken(); // consume the (

          // Parse an expression and make its node the root node.
          rootNode = parseExpression(token);
          TypeSpec resultType =
              rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;

          // Look for the matching ) token.
          token = currentToken();
          if (token.getType() == RIGHT_PAREN) token = nextToken(); // consume the )
          else errorHandler.flag(token, MISSING_RIGHT_PAREN, this);
          rootNode.setTypeSpec(resultType);
          break;
        }

      default:
        {
          errorHandler.flag(token, UNEXPECTED_TOKEN, this);
          break;
        }
    }
    return rootNode;
  }
Example #4
0
  /**
   * Parse a simple expression.
   *
   * @param token the initial token.
   * @return the root of the generated parse subtree.
   * @throws Exception if an error occurred.
   */
  private ICodeNode parseSimpleExpression(Token token) throws Exception {
    Token signToken = null;
    TokenType signType = null; // type of leading sign (if any)

    // Look for a leading + or - sign
    TokenType tokenType = token.getType();
    if ((tokenType == PLUS) || (tokenType == MINUS)) {
      signType = tokenType;
      signToken = token;
      token = nextToken(); // consume the + or -
    }

    // Parse a term and make the root of its tree the root node.
    ICodeNode rootNode = parseTerm(token);
    TypeSpec resultType = rootNode != null ? rootNode.getTypeSpec() : Predefined.undefinedType;

    // Type check: Leading sign.
    if ((signType != null) && (!TypeChecker.isIntegerOrReal(resultType)))
      errorHandler.flag(signToken, INCOMPATIBLE_TYPES, this);

    // Was there a leading - sign?
    if (signType == MINUS) {
      // Create a NEGATE node and adopt the current tree as its child.
      // The NEGATE node becomes the new root node.
      ICodeNode negateNode = ICodeFactory.createICodeNode(NEGATE);
      negateNode.addChild(rootNode);
      negateNode.setTypeSpec(rootNode.getTypeSpec());
      rootNode = negateNode;
    }

    token = currentToken();
    tokenType = token.getType();

    // Loop over additive operators.
    while (ADD_OPS.contains(tokenType)) {
      TokenType operator = tokenType;

      // Create a new operator node and adopt the current tree as its first child.
      ICodeNodeType nodeType = ADD_OPS_OPS_MAP.get(operator);
      ICodeNode opNode = ICodeFactory.createICodeNode(nodeType);
      opNode.addChild(rootNode);

      token = nextToken(); // consume the operator

      // Parse another term.
      // The operator node adopts the term's tree as its second child.
      ICodeNode termNode = parseTerm(token);
      opNode.addChild(termNode);
      TypeSpec termType = termNode != null ? termNode.getTypeSpec() : Predefined.undefinedType;

      // The operator node becomes the new root node.
      rootNode = opNode;

      switch ((PascalTokenType) operator) {
        case PLUS:
        case MINUS:
          {
            // Both operands integer => integer result.
            if (TypeChecker.areBothInteger(resultType, termType))
              resultType = Predefined.integerType;

            // Both real operands or one real and one integer operand => real result.
            else if (TypeChecker.isAtLeastOneReal(resultType, termType))
              resultType = Predefined.realType;
            else errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            break;
          }

        case OR:
          {
            // Both operands boolean ==> boolean result.
            if (TypeChecker.areBothBoolean(resultType, termType))
              resultType = Predefined.booleanType;
            else errorHandler.flag(token, INCOMPATIBLE_TYPES, this);
            break;
          }
      }

      rootNode.setTypeSpec(resultType);
      token = currentToken();
      tokenType = token.getType();
    }
    return rootNode;
  }