24 lines
457 B
Text
24 lines
457 B
Text
open nat
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open eq.ops
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inductive even : nat → Prop :=
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even_zero : even zero,
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even_succ_of_odd : ∀ {a}, odd a → even (succ a)
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with odd : nat → Prop :=
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odd_succ_of_even : ∀ {a}, even a → odd (succ a)
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example : even 1 → false :=
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begin
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intro He1,
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cases He1 with (a, Ho0),
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cases Ho0
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end
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example : even 3 → false :=
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begin
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intro He3,
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cases He3 with (a, Ho2),
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cases Ho2 with (a, He1),
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cases He1 with (a, Ho0),
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cases Ho0
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end
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