English
EquicontinuousWithinAt is equivalent to the stated universal property with nhdsWithin, i.e., an equivalence with nhdsWithin x0 on S.
Русский
EquicontinuousWithinAt эквивалентно свойству существования окружения nhdsWithin x0 на S.
LaTeX
$$$EquicontinuousWithinAt(F,S,x_0) \iff (∀ U ∈ 𝓤(α), U\text{–покрытие}, 𝓕)$. (formal equivalence with nhdsWithin)$$
Lean4
/-- A family `F : ι → X → α` of functions from a topological space to a uniform space is
*equicontinuous* on all of `X` if it is equicontinuous at each point of `X`. -/
def Equicontinuous (F : ι → X → α) : Prop :=
∀ x₀, EquicontinuousAt F x₀