import numpy as np

from sherpa.astro import xspec
from sherpa.models.basic import PowLaw1D

_hc = 6.6260693e-27 * 2.99792458e+18 / 1.60217653e-9

elo = np.asarray([0.1, 0.2, 0.5, 0.6])
ehi = np.asarray([0.2, 0.3, 0.6, 0.7])

wlo = _hc / ehi
whi = _hc / elo

mdl1 = xspec.XSpowerlaw()
mdl2 = PowLaw1D()

ey1 = mdl1(elo, ehi)
ey2 = mdl2(elo, ehi)

wy1 = mdl1(wlo, whi)
wy2 = mdl2(wlo, whi)

if (ey1 != ey2).any():
    print("Energy difference")

if np.abs(ey2 - wy2).max() > 1e-12:
    print("Wavelength difference")

print("wy1: {}".format(wy1))
print("wy2: {}".format(wy2))