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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
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15 include "ground/arith/pnat_minus.ma".
16 include "ground/arith/pnat_lt.ma".
17 include "ground/arith/nat_minus.ma".
19 (* SUBTRACTION FOR NON-NEGATIVE INTEGERS ************************************)
21 (* Constructions with pminus ************************************************)
23 lemma nminus_inj_bi (p1) (p2):
25 ninj (p1 - p2) = ninj p1 - ninj p2.
26 #p2 #p1 #H0 @(plt_ind_alt … H0) -p1 -p2 //