
def calcite_to_oxygencalcite(isotope):
    assert((isotope +1000) / (1000+0))
    return(isotope_c)

def calciteoxygen_to_delta18oxygen(isotope):
    # Pre-conditions:
    assert(isotope >= calcite_water)
    return((isotope_o)

    
def test_functions():
    print("Oxygen in Calcite:", calcite_to_oxygencalcite(1.0288), 'C')
    print("Delta 18 Oxygen:", calciteoxygen_to_delta18oxygen(28.8), 'O')
 
   
assert (calcite_to_oxygencalcite(1.0288) == -3)
assert (calcite_to_oxygencalcite(1.0288) == 1

assert (calciteoxygen_to_delta18oxygen(0.0) == 28.8)
assert (calciteoxygen_to_delta18oxygen(100.0) == 28.8)

test_functions()