  We present the numerically exact ground state energy, effective mass, and
isotope exponents of a one-dimensional lattice polaron, valid for any range of
electron-phonon interaction, applying a new continuous-time Quantum Monte Carlo
(QMC) technique in a wide range of coupling strength and adiabatic ratio. The
QMC method is free from any systematic finite-size and finite-time-step errors.
We compare our numerically exact results with analytical weak-coupling theory
and with the strong-coupling $1/\lambda$ expansion. We show that the exact
results agree well with the canonical Fr\"ohlich and Holstein-Lang-Firsov
theories in the weak and strong coupling limits, respectively, for any range of
interaction. We find a strong dependence of the polaron dynamics on the range
of interaction. An increased range of interaction has a similar effect to an
increased (less adiabatic) phonon frequency: specifically, a reduction in the
effective mass.
