Section FormationLemmas.
Variable (f g : {finMap K -> V}).
End FormationLemmas.
Implicit Types (k : K) (v : V) (f g : base).

Lemma umapE (f g : base) :
f = g <-> match f, g with
Def f' pf, Def g' pg => f' = g'
| Undef, Undef => true
| _, _ => false
end.