Fixpoint mkInjectionsN (N:nat)(n1 n2:block)(j k l: meminj)
:  meminj * meminj * block * block :=
match N with O => (j,k,n1,n2)
| S M => mkInjectionsN M (Pos.succ n1) (Pos.succ n2)
(fun b => if eq_block b n1
then Some (n2,0)
else j b)
(fun b => if eq_block b n2 then l n1 else k b)
l
end.

Lemma mkInjectionsN_2: forall N n1 n2 j k l j' k' n1' n2'
(HI: mkInjectionsN N n1 n2 j k l = (j',k',n1',n2')),
forall b2 b3 ofs3 (Jb: k b2 = Some(b3,ofs3)),
(b2 < n2)%positive -> k' b2 = Some (b3,ofs3).