Section FunPlainTheory.
Variables (aT : finType) (rT : Type).
Notation fT := {ffun aT -> rT}.
Implicit Types (f : fT) (R : pred rT).
Definition fgraph f := codom_tuple f.
Definition Finfun (G : #|aT|.-tuple rT) := [ffun x => tnth G (enum_rank x)].

Lemma tnth_fgraph f i : tnth (fgraph f) i = f (enum_val i).