ishftc returns a value corresponding to i with the rightmost size bits shifted circularly shift places; that is, bits shifted out one end are shifted into the opposite end. A value of shift greater than zero corresponds to a left shift, a value of zero corresponds to no shift, and a value less than zero corresponds to a right shift. The absolute value of shift must be less than size. If the size argument is omitted, it is taken to be equivalent to bit_size(i).