def get_scaling_function(y_m, y_M, x_m, x_M):
    """
    Returns a linear function y = k x + b, where y \\in [m, M]
    :param y_m:
    :param y_M:
    :param x_m:
    :param x_M:
    :return:
    """
    if x_M <= x_m:
        return lambda _: y_m
    k = (y_M - y_m) / (x_M - x_m)
    b = y_m - k * x_m
    return lambda _: int(k * _ + b)
