matita/matita/contribs/lambdadelta/ground_2/lib/bool.ma

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  14
  15 include "basics/bool.ma".
  16 include "ground_2/notation/constructors/no_0.ma".
  17 include "ground_2/notation/constructors/yes_0.ma".
  18
  19 (* BOOLEAN PROPERTIES *******************************************************)
  20
  21 interpretation "boolean false" 'no = false.
  22
  23 interpretation "boolean true" 'yes = true.
  24
  25 lemma orb_false_r: ∀b1,b2:bool. (b1 ∨ b2) = false → b1 = false ∧ b2 = false.
  26 * normalize /2 width=1 by conj/ #b2 #H destruct
  27 qed-.
  28
  29 lemma commutative_orb: commutative … orb.
  30 * * // qed.