lean2/tests/lean/calc_assistant.lean

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import logic
open eq.ops
set_option elaborator.calc_assistant false
theorem tst1 (a b c : num) (H₁ : ∀ x, b = x) (H₂ : c = b) : a = c :=
calc a = b : H₁ -- error because calc assistant is off
... = c : H₂
theorem tst2 (a b c : num) (H₁ : ∀ x, b = x) (H₂ : c = b) : a = c :=
calc a = b : !H₁⁻¹
... = c : H₂ -- error because calc assistant is off
theorem tst3 (a b c : num) (H₁ : ∀ x, b = x) (H₂ : c = b) : a = c :=
calc a = b : !H₁⁻¹
... = c : H₂⁻¹
theorem tst4 (a b c : num) (H₁ : ∀ x, b = x) (H₂ : c = b) : a = c :=
calc a = b : eq.symm (H₁ a)
... = c : eq.symm H₂
set_option elaborator.calc_assistant true
theorem tst5 (a b c : num) (H₁ : ∀ x, b = x) (H₂ : c = b) : a = c :=
calc a = b : H₁
... = c : H₂