English
The dilation of a set s by a scalar a is the image of s under the map y ↦ a • y.
Русский
Расширение множества s скаляром a — это образ множества s при отображении y ↦ a • y.
LaTeX
$$$$ \mathrm{smulSet}(a,s) = \{ a \cdot y : y \in s \} $$$$
Lean4
/-- The dilation of set `x • s` is defined as `{x • y | y ∈ s}` in scope `Pointwise`. -/
@[to_additive /-- The translation of set `x +ᵥ s` is defined as `{x +ᵥ y | y ∈ s}` in scope `Pointwise`. -/
]
protected def smulSet [SMul α β] : SMul α (Set β) where smul a := image (a • ·)