12 lines
309 B
Text
12 lines
309 B
Text
class Monoid (α : Type u) [Zero α] extends Add α where
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zero_add (a : α) : 0 + a = a
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add_zero (a : α) : a + 0 = a
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attribute [simp] Monoid.zero_add Monoid.add_zero
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variable {α : Type u} [Zero α] [Monoid α]
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-- works
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example (a : α) : 0 + a = a := by simp
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example (a : α) : a + 0 = a := by simp
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