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LeifW/NatAssoc.idr

Created September 29, 2016 05:21
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Natural number associativity proof in tactics and editor commands
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NatAssoc.idr
natAssoc1 : (x, y, z : Nat) -> x + (y + z) = (x + y) + z
natAssoc1 = ?natAssocProof
natAssocProof = proof
intros
induction x
trivial
intros
compute
rewrite ihn__0
trivial
natAssoc2 : (x, y, z : Nat) -> x + (y + z) = (x + y) + z
natAssoc2 Z y z = Refl
natAssoc2 (S k) y z = cong {f = S} $ natAssoc2 k y z
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