a6888f72dd
The following could not be elaborated.
```lean
instance : MulComm Bool where
mulComm := fun {a b} =>
match a, b with
| true, true => rfl
| true, false => rfl
| false, true => rfl
| false, false => rfl
```
64 lines
1.4 KiB
Text
64 lines
1.4 KiB
Text
class MulComm (α : Type u) [Mul α] : Prop where
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mulComm : {a b : α} → a * b = b * a
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instance : Mul Bool where
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mul := and
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instance : MulComm Bool where
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mulComm {a b} :=
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl
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instance : MulComm Bool where
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mulComm := fun {a b} =>
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl
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instance : MulComm Bool := {
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mulComm := fun {a b} =>
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl
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}
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instance : MulComm Bool := {
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mulComm := @fun a b =>
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl
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}
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instance : MulComm Bool where
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mulComm {a b} := by cases a <;> cases b <;> rfl
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instance : MulComm Bool :=
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⟨by intro a b; cases a <;> cases b <;> rfl⟩
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instance : MulComm Bool :=
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⟨fun {a b} => by cases a <;> cases b <;> rfl⟩
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instance : MulComm Bool :=
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⟨fun {a b} =>
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl⟩
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instance : MulComm Bool :=
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⟨@fun a b =>
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match a, b with
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| true, true => rfl
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| true, false => rfl
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| false, true => rfl
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| false, false => rfl⟩
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