English
If SMulCommClass M N α and SMulCommClass M N β hold, then SMulCommClass M N (Sum α β) holds.
Русский
Если существуют SMulCommClass M N α и SMulCommClass M N β, то SMulCommClass M N (Sum α β) выполняется.
LaTeX
$$$[SMulCommClass M N α][SMulCommClass M N β] \Rightarrow SMulCommClass M N (Sum α β).$$$
Lean4
@[to_additive]
instance [SMulCommClass M N α] [SMulCommClass M N β] : SMulCommClass M N (α ⊕ β) :=
⟨fun a b x => by
cases x
exacts [congr_arg inl (smul_comm _ _ _), congr_arg inr (smul_comm _ _ _)]⟩