|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 15257). This is not the
same as defining a specific function's mapping, which is typically done
using the format of cmpt 5041 with the maps-to notation (see df-mpt 5042 and
df-mpo 7021). Contrast this predicate with the
predicates to determine if
some class is a function with a given domain (df-fn 6228), a function
with a given domain and codomain (df-f 6229), a one-to-one function
(df-f1 6230), an onto function (df-fo 6231), or a one-to-one onto function
(df-f1o 6232). For alternate definitions, see dffun2 6235, dffun3 6236,
dffun4 6237, dffun5 6238, dffun6 6240, dffun7 6252, dffun8 6253, and dffun9 6254.
(Contributed by NM, 1-Aug-1994.)|