def calc(self, t):
    '\n        Calc position\n        if t is outside of the input x, return None\n        '
    if (t < self.x[0]):
        return None
    elif (t > self.x[(- 1)]):
        return None
    i = self.__search_index(t)
    dx = (t - self.x[i])
    result = (((self.a[i] + (self.b[i] * dx)) + (self.c[i] * (dx ** 2.0))) + (self.d[i] * (dx ** 3.0)))
    return result
Calc position
if t is outside of the input x, return None
def calc(self, t):
    '\n        Calc position\n        if t is outside of the input x, return None\n        '
    if (t < self.x[0]):
        return None
    elif (t > self.x[(- 1)]):
        return None
    i = self.__search_index(t)
    dx = (t - self.x[i])
    result = (((self.a[i] + (self.b[i] * dx)) + (self.c[i] * (dx ** 2.0))) + (self.d[i] * (dx ** 3.0)))
    return result