Description: Define predicate that
determines if some class A is a function.
Definition 10.1 of [Quine] p. 65. For
example, the expression
Fun I is true (funi 4875). This is not the same as defining a
specific function's mapping, which is typically done using the format of
cmpt 3809 with the maps-to notation (see df-mpt 3811). Contrast this
predicate with the predicates to determine if some class is a function
with a given domain (df-fn 4848), a function with a given domain and
codomain (df-f 4849), a one-to-one function (df-f1 4850), an onto function
(df-fo 4851), or a one-to-one onto function (df-f1o 4852). For alternate
definitions, see dffun2 4855, dffun4 4856, dffun6 4859, dffun7 4871, dffun8 4872,
and dffun9 4873. (Contributed by NM,
1-Aug-1994.) |