Description: Define the value of an
operation. Definition of operation value in
[Enderton] p. 79. Note that the syntax
is simply three class expressions
in a row bracketed by parentheses. There are no restrictions of any kind
on what those class expressions may be, although only certain kinds of
class expressions - a binary operation and its arguments and
- will be useful for proving meaningful theorems.
For example, if
class is the operation and arguments and are
and , the expression can be proved to equal (see
3p2e510693). This definition is well-defined, although
not very meaningful,
when classes and/or are proper classes (i.e. are not sets);
see ovprc16327 and ovprc26328. On the other hand, we often find uses for
this definition when is a proper class, such as
in oav7180.
is normally equal to a class of nested ordered
pairs of the form
defined by df-oprab6300. (Contributed by NM,
28-Feb-1995.)