import math


def lafferty_wyatt_point(lowedge, highedge, expo_slope):
    """calculates the l-w point for a bin where the true distribution is an
    exponential characterized by expo_slope.
    """
    rhs = (math.exp(expo_slope*highedge) - math.exp(expo_slope*lowedge)) 
    rhs /= expo_slope
    rhs /= (highedge - lowedge)
    return math.log(rhs) / expo_slope