Valloud Andres <Andres.Valloud at oya.state.or.us> argued that
	x\x and xUx are not equivalent to removeAll: and addAll: because \ and U
	don't mutate the contents of x.
	
x \:= x   and   x U:= x
*are* translation equivalents of (x addAll: x) and (x removeAll: x)
(when x is a Set or a CharacterSet or a Bag).

In SETL, for example, these operations existed,
and did not make lhs==rhs a special case (and didn't need to).

Does one really have to spell out every single pedantic detail?
x\x and xUx were relevant to what the final state of the receiver
should be; the point is that a state equivalent to those should be reached.