abstractsyntaxnode.java

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     */
    static boolean matchBooleanLiteral(Scanner s) throws ParserException,
            ScannerException {
        Token t = s.token();

        if (!t.isBooleanLiteral())
            parserError(t, "Boolean literal expected");

        s.advance();

        return ((BooleanLiteralToken) t).content();
    }

    /**
     * If the next token is a <b>number literal </b> the scanner moves on to the
     * next token and the matched token is returned.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @throws ParserException
     *             If the token doesn't match.
     * @return the matched token
     * @see NumberLiteralToken
     */
    static int matchNumberLiteral(Scanner s) throws ParserException,
            ScannerException {
        Token t = s.token();

        if (!t.isNumberLiteral())
            parserError(t, "Number literal expected");

        s.advance();

        return ((NumberLiteralToken) t).content();
    }

    /**
     * If the next token is a <b>simple token </b> true is returned. The scanner
     * does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see SimpleToken
     */
    static boolean isSimpleToken(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isSimple();
    }

    /**
     * If the next token is a <b>bracket </b> true is returned. The scanner does
     * not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see BracketToken
     */
    static boolean isBracketToken(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isBracket();
    }

    /**
     * If the next token is an <b>operator </b> true is returned. The scanner
     * does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see OperatorToken
     */
    static boolean isOperatorToken(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isOperator();
    }

    /**
     * If the next token is a <b>keyword </b> true is returned. The scanner does
     * not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see KeywordToken
     */
    static boolean isKeywordToken(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isKeyword();
    }

    /**
     * If the next token is an <b>identifier </b> true is returned. The scanner
     * does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see IdentifierToken
     */
    static boolean isIdentifierToken(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isIdentifier();
    }

    /**
     * If the next token is a <b>boolean literal </b> true is returned. The
     * scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see BooleanLiteralToken
     */
    static boolean isBooleanLiteral(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isBooleanLiteral();
    }

    /**
     * If the next token is a <b>number literal </b> true is returned. The
     * scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the token type matches, false if not
     * @see NumberLiteralToken
     */
    static boolean isNumberLiteral(Scanner s) throws ScannerException {
        Token t = s.token();
        return t.isNumberLiteral();
    }

    /**
     * Returns true if the next token is a <b>simple token </b> and matches the
     * given char. The scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the type and token match, false if not
     * @see SimpleToken
     */
    static boolean isSimpleToken(Scanner s, char c) throws ScannerException {
        Token t = s.token();

        if (t.isSimple())
            return ((SimpleToken) t).content() == c;

        return false;
    }

    /**
     * Returns true if the next token is a <b>bracket </b> and matches the given
     * char. The scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the type and token match, false if not
     * @see BracketToken
     */
    static boolean isBracketToken(Scanner s, char c) throws ScannerException {
        Token t = s.token();

        if (t.isBracket())
            return ((BracketToken) t).content() == c;

        return false;
    }

    /**
     * Returns true if the next token is an <b>operator </b> and matches the
     * given char. The scanner does not move to the next token. According to
     * <code>OperatorToken</code> the operators "&&", "||", "==" are
     * represented by '&', '|', '='.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the type and token match, false if not
     * @see OperatorToken
     */
    static boolean isOperatorToken(Scanner s, char c) throws ScannerException {
        Token t = s.token();

        if (t.isOperator())
            return ((OperatorToken) t).content() == c;

        return false;
    }

    /**
     * Returns true if the next token is a <b>keyword </b> and matches the given
     * char. The scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the type and token match, false if not
     * @see KeywordToken
     */
    static boolean isKeywordToken(Scanner s, String w) throws ScannerException {
        Token t = s.token();

        if (t.isKeyword())
            return ((KeywordToken) t).content().equals(w);

        return false;
    }

    /**
     * Returns true if the next token is an <b>identifier </b> and matches the
     * given char. The scanner does not move to the next token.
     * 
     * @param s
     *            reference to the scanner returning the tokens.
     * @throws ScannerException
     *             If an input error occured
     * @return true, if the type and token match, false if not
     * @see IdentifierToken
     */
    static boolean isIdentifierToken(Scanner s, String value)
            throws ScannerException {
        Token t = s.token();

        if (t.isIdentifier())
            return ((IdentifierToken) t).content().equals(value);

        return false;
    }

    /**
     * Throws a ParserException with the line of the given token, its position
     * and the given error description.
     * 
     * @param currentToken
     *            the token which created the parsing error
     * @param errorDescription
     *            an error description
     * @throws ParserException
     *             the generated exception
     * @see ParserException
     */
    static void parserError(Token currentToken, String errorDescription)
            throws ParserException {
        throw new ParserException(currentToken.line(), currentToken.pos(),
                errorDescription);
    }

    /**
     * Throws an InterpreterException created from the given error description.
     * 
     * @param errorDescription
     *            an error description
     * @throws InterpreterException
     *             the generated exception
     * @see InterpreterException
     */
    static void interpreterError(String errorDescription)
            throws InterpreterException {
        throw new InterpreterException(errorDescription);
    }
}