Returns the least significant width bits of this integer, extending the
highest retained bit to the sign. This is the same as truncating the
value to fit in width bits using an signed 2-s complement
representation.
The returned value has the same bit value in all positions higher than
width.

Returns the least significant width bits of this integer as a
non-negative number (i.e. unsigned representation). The returned value
has zeros in all bit positions higher than width.