def computeDeriv(poly):
    '''
    Computes and returns the derivative of a polynomial function as a list of
    floats. If the derivative is 0, returns [0.0].

    poly: list of numbers, length > 0
    returns: list of numbers (floats)
    '''
    f = 0.0
    L=[0.0]
    for i in range(len(poly)):
        f = float(poly[i] * i)
        if i >= 1:
#            f = (poly[i] * i)
            L.append(f)
    return L