Declaration
mainvarYou may declare variables to be mainvar. The ordering
scale for atoms is essentially: numbers < constants (e.g., %e, %pi) <
scalars < other variables < mainvars. E.g., compare expand ((X+Y)^4)
with (declare (x, mainvar), expand ((x+y)^4)). (Note: Care should be
taken if you elect to use the above feature. E.g., if you subtract an
expression in which x is a mainvar from one in which x isn't a
mainvar, resimplification e.g. with ev (expr, simp) may be
necessary if cancellation is to occur. Also, if you save an
expression in which x is a mainvar, you probably should also save x.)