English
As x approaches from the left, fract tends to 1 with x approaching an integer from below, in the fract-topology sense.
Русский
При подходе слева fract стремится к 1, когда x приближается к целому снизу.
LaTeX
$$$$\lim_{y \to x^-} \operatorname{fract}(y) = 1.$$$$
Lean4
theorem tendsto_ceil_right (n : ℤ) : Tendsto (fun x => ceil x : α → α) (𝓝[>] n) (𝓝[≥] (n + 1)) :=
((tendsto_pure_pure _ _).comp (tendsto_ceil_right_pure_add_one n)).mono_right <| by rw [← @cast_one α, ← cast_add];
exact pure_le_nhdsWithin le_rfl