for f being PartFunc of REAL,REAL
for x0 being Real st f is_left_convergent_in x0 holds
( ex r being Real st
( 0 < r & f | ].(x0 - r),x0.[ is bounded_below ) & ex r being Real st
( 0 < r & f | ].(x0 - r),x0.[ is bounded_above ) )