English
A left-cancelative monoid yields a faithful action on the opposite monoid by left action.
Русский
Левостороннее отменяемое моноид обеспечивает верное действие на противоположном моноиде левым действием.
LaTeX
$$$\\text{to_faithfulSMul_mulOpposite }[LeftCancelMonoid \\alpha] : \\text{FaithfulSMul } \\alpha^{\\mathrm{op}} \\alpha$$$
Lean4
/-- `Monoid.toOppositeMulAction` is faithful on cancellative monoids. -/
@[to_additive /-- `AddMonoid.toOppositeAddAction` is faithful on additive cancellative monoids. -/
]
instance to_faithfulSMul_mulOpposite [LeftCancelMonoid α] : FaithfulSMul αᵐᵒᵖ α :=
⟨fun h ↦ MulOpposite.unop_injective <| mul_left_cancel (h 1)⟩