Description: Define predicate that
determines if some class is a function.
Definition 10.1 of [Quine] p. 65. For
example, the expression
is true (funi 4932). This is not the same as defining a
specific function's mapping, which is typically done using the format of
cmpt 3818 with the maps-to notation (see df-mpt 3820). Contrast this
predicate with the predicates to determine if some class is a function
with a given domain (df-fn 4905), a function with a given domain and
codomain (df-f 4906), a one-to-one function (df-f1 4907), an onto function
(df-fo 4908), or a one-to-one onto function (df-f1o 4909). For alternate
definitions, see dffun2 4912, dffun4 4913, dffun6 4916, dffun7 4928, dffun8 4929,
and dffun9 4930. (Contributed by NM,
1-Aug-1994.) |