The orthopoly unit_step function autoloads (see src/max_ext.lisp); try
this:
(%i1) trace(?load, load)$
(%i2) map('unit_step,[-1,0,1]);
1 Enter ?load [/5.16.3/share/orthopoly/orthopoly.lisp]
(%o2) [0,0,1]
If you redefine unit_step to be right continuous, you'll break a few things
in orthopoly.
Barton