[racket] Tricky case of occurrence typing in Typed Racket

Andrew Kent writes:

 > Will andmap work for you?

Interesting... I didn't know about that one.

For my demonstration code, that's indeed a good solution. In my real
application, the test is more complicated. I need to check all
elements of a list for conformance to a union type, so I have no
prefabricated predicate, not even for the elements of my list.

Konrad.