An expression is of type And(type1, type2, ...) if it is all of the types type1, type2, ... .

An expression is of type Or(type1, type2, ...) if it is one of the types type1, type2, ... . Note the Or(type1, type2, ...) is equivalent to  but the type checks always occur in order.  This may be useful if it is known that one type check is faster than a second.

An expression is of type Not(type1) if it is not of type type1. Non(type1) is equivalent to Not(type1).