def lerp(start, stop, amount):
    """Linearly interpolate the start value to the stop value.

    Examples ::

        >>> lerp(0, 10, 0.0)
        0.0

        >>> lerp(0, 10, 0.5)
        5.0

        >>> lerp(0, 10, 0.8)
        8.0

        >>> lerp(0, 10, 1.0)
        10.0

    :param start: The start value

    :param stop: The stop value

    :param amount: The amount by which to interpolate. (:math:`0 \\leq
        amount \\leq 1`).
    :type amount: float

    """
    return start + amount * (stop - start)
