|Description: Define predicate that
determines if some class 𝐴 is a function.
Definition 10.1 of [Quine] p. 65. For
example, the expression
Fun cos is true once we define cosine (df-cos 12711). This is not the
same as defining a specific function's mapping, which is typically done
using the format of cmpt 4297 with the maps-to notation (see df-mpt 4299 and
df-mpt2 6122). Contrast this predicate with the
predicates to determine
if some class is a function with a given domain (df-fn 5492), a function
with a given domain and codomain (df-f 5493), a one-to-one function
(df-f1 5494), an onto function (df-fo 5495), or a one-to-one onto function
(df-f1o 5496). For alternate definitions, see dffun2 5499, dffun3 5500,
dffun4 5501, dffun5 5502, dffun6 5504, dffun7 5514, dffun8 5515, and dffun9 5516.
(Contributed by NM, 1-Aug-1994.)|