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 5230). This is not the same as defining a
specific function's mapping, which is typically done using the format of
cmpt 4050 with the maps-to notation (see df-mpt 4052). Contrast this
predicate with the predicates to determine if some class is a function
with a given domain (df-fn 5201), a function with a given domain and
codomain (df-f 5202), a one-to-one function (df-f1 5203), an onto function
(df-fo 5204), or a one-to-one onto function (df-f1o 5205). For alternate
definitions, see dffun2 5208, dffun4 5209, dffun6 5212, dffun7 5225, dffun8 5226,
and dffun9 5227. (Contributed by NM,
1-Aug-1994.) |