English
The product of a pure filter at a with any filter g is the pushforward of g along a, i.e., (pure a) • g = map (a • ·) g.
Русский
Произведение чистого фильтра на a и фильтра g эквивалентно образу переноса фильтра g по действию a: (pure a) • g = map (a • ·) g.
LaTeX
$$$(\text{pure } a) \cdot g = g \mapsto (a \cdot \;)$$
Lean4
@[to_additive (attr := simp)]
theorem pure_smul : (pure a : Filter α) • g = g.map (a • ·) :=
map₂_pure_left