The *other* major computer symbolic algebra system (apart from Mathematica)
which seems to have not quite as much traction because of… not having a messianic CEO?
Having awful branding?
It seems to be OK now that I look at it.
In particular, it does what I expect regarding transforms of random variables.

Since everyone seems to know Mathematica, I guess I should describe it in terms of that? It is imperative-emphasis rather than functional emphasis; the upshot seems to be that if you want functional behaviour it has to be defined using the “inert” form?