The general simplifier currently treats the various non-
standard objects (inf, minf, und, ind, infinity) as though
they were ordinary variables.
This leads to incorrect results (inf-inf => 0, inf*0 => 0),
incomplete simplification (inf^3 doesn't simplify, though
inf is always correct), and non-canonical representations
(-minf doesn't simplify to inf).
It also seems to me that minf should be represented
uniformly as -inf, not as a special case.
Special-casing these objects in the general simplifier will
add a very small overhead to all simplifications.
The case that reminded me of this problem is abs(minf)