English
Copying a submonoid along an equal carrier yields the same submonoid.
Русский
Копирование подмономиода вдоль эквивалентного носителя даёт тот же подмономиод.
LaTeX
$$$$ S\\,copy\\, s\\, hs = S $$$$
Lean4
/-- Copy a submonoid replacing `carrier` with a set that is equal to it. -/
@[to_additive /-- Copy an additive submonoid replacing `carrier` with a set that is equal to it. -/
]
protected def copy (S : Submonoid M) (s : Set M) (hs : s = S) : Submonoid M
where
carrier := s
one_mem' := show 1 ∈ s from hs.symm ▸ S.one_mem'
mul_mem' := hs.symm ▸ S.mul_mem'