Lean4
/-- The piecewise multiplication from the `Mul` instance, as a bundled homomorphism. -/
@[simps]
def gMulHom {i j} : A i →+ A j →+ A (i + j)
where
toFun
a :=
{ toFun := fun b => GradedMonoid.GMul.mul a b
map_zero' := GNonUnitalNonAssocSemiring.mul_zero _
map_add' := GNonUnitalNonAssocSemiring.mul_add _ }
map_zero' := AddMonoidHom.ext fun a => GNonUnitalNonAssocSemiring.zero_mul a
map_add' _ _ := AddMonoidHom.ext fun _ => GNonUnitalNonAssocSemiring.add_mul _ _ _