If the current position doesn't hold the specified c character then it raises an
        exception, otherwise it skips the specified character (moves the current position forward).

def expect(self, c):
        """
        If the current position doesn't hold the specified c character then it raises an
        exception, otherwise it skips the specified character (moves the current position forward).
        """
        if self.peek() != c:
            self.error('Expected "%c"' % (c,))
        self.skip_char()