undo-elt-in-region

undo-elt-in-region is a compiled Lisp function in `simple.el'.

(undo-elt-in-region UNDO-ELT START END)

Determine whether UNDO-ELT falls inside the region START ... END.
If it crosses the edge, we return nil.

Generally this function is not useful for determining
whether (MARKER . ADJUSTMENT) undo elements are in the region,
because markers can be arbitrarily relocated. Instead, pass the
marker adjustment's corresponding (TEXT . POS) element.