English
For a structured arrow with domain U, the functor sends it to its generator an element of X.
Русский
Для структурированной стрелы с доменом U функтор отправляет ее в свой генератор, элемент X.
LaTeX
$$$\mathrm{generator}(U) \in X$$$
Lean4
/-- Given a structured arrow `f` with domain `U : Opens X` over `principals X`,
this functor sends `f` to its "generator", an element of `X`. -/
abbrev generator (U : Opens X) : StructuredArrow (.op U) (principals X) ⥤ X :=
StructuredArrow.proj (.op U) (principals X)