EV ratdisreps any CRE subexpressions in its input,
including in atoms (and re-RATs the result). The precise
statement of when it ratdisreps is (as usual with EV)
hard to express without talking about the implementation.
This should be documented.
Examples:
ex: rat(%i)^2$
ev(ex) => -1 /R/
ev([ex]) => [-1]
ev(''(rat(%i)^2)) => -1 /R/ (two single-quotes)
but
ev(rat(%i)^2) => %i^2 /R/
Now here's an interesting case:
expr: '( factor(x^2-1) )$ /R/
ev(expr) => x^2-1 /R/
Ha Ha! It noticed that the input was in CRE form,
so it Rat'ed the output... compare:
ratfac:true$
ev(expr) => (x-1)*(x+1) /R/
