29 lines
618 B
Text
29 lines
618 B
Text
open tactic
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meta def my_tac : tactic unit :=
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assumption <|> abstract (comp_val >> skip) <|> fail "my_tac failed to synthesize auto_param"
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def f (x : nat) (h : x > 0 . my_tac) : nat :=
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nat.pred x
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check f 12
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check f 13
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lemma f_inj {x₁ x₂ : nat} {h₁ : x₁ > 0} {h₂ : x₂ > 0} : f x₁ = f x₂ → x₁ = x₂ :=
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begin
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unfold f, intro h,
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cases x₁,
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exact absurd h₁ (lt_irrefl _),
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cases x₂,
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exact absurd h₂ (lt_irrefl _),
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apply congr_arg nat.succ,
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assumption
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end
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check @f_inj
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lemma f_def {x : nat} (h : x > 0) : f x = nat.pred x :=
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rfl
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-- The following is an error
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-- check λ x, f x
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