private Token _readtok() throws IOException {
		while (Character.isWhitespace(currCh) && !eof) {
			readch();
		}
		if (eof) return EOF;
		if (currCh == '(' || currCh == ')') {
			char c = currCh;
			readch();
			return new Token(c + "", Token.Type.SYNCON);
		}
		else {
			String s = "";
			do {
				s += currCh;
			} while (readch() && !Character.isWhitespace(currCh) && currCh != '(' && currCh != ')');
			return new Token(s, Token.Type.IDENTIFIER);
		}
	}