Section selectors.
Variable (j: juicy_mem).
Definition m_dry := match j with mkJuicyMem m _ _ _ _ _ => m end.
Definition m_phi := match j with mkJuicyMem _ phi _ _ _ _ => phi end.

Lemma constructive_age1_join  {A}  {JA: Join A}{PA: Perm_alg A}{agA: ageable A}{AgeA: Age_alg A} : forall x y z x' : A,
join x y z ->
age x x' ->
{ yz' : A*A | join x' (fst yz') (snd yz') /\ age y (fst yz') /\ age z (snd yz')}.