18 lines
442 B
Text
18 lines
442 B
Text
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import logic num
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using num eq_proofs
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inductive nat : Type :=
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| zero : nat
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| succ : nat → nat
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definition add (x y : nat) : nat := nat_rec x (λn r, succ r) y
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infixl `+`:65 := add
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definition mul (n m : nat) := nat_rec zero (fun m x, x + n) m
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infixl `*`:75 := mul
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axiom mul_succ_right (n m : nat) : n * succ m = n * m + n
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theorem small2 (n m l : nat) : n * succ l + m = n * l + n + m
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:= subst (mul_succ_right _ _) (refl (n * succ l + m))
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