प्रोग्राम की सुविधाएँ · रुंगे–कुट्टा क्षय चरण

def decay_steps(initial, rate, dt, steps):
    if any(type(v) not in (int, float) for v in (initial, rate, dt)):
        raise ValueError("decay.numeric")
    if not -10**6 <= initial <= 10**6 or not 0 <= rate <= 1000 or not 0 <= dt <= 1 or rate * dt > 1:
        raise ValueError("decay.range")
    if type(steps) is not int or not 0 <= steps <= 1000:
        raise ValueError("decay.steps")
    y = float(initial)
    for _ in range(steps):
        k1 = -rate * y
        k2 = -rate * (y + dt*k1/2)
        k3 = -rate * (y + dt*k2/2)
        k4 = -rate * (y + dt*k3)
        y += dt*(k1 + 2*k2 + 2*k3 + k4)/6
    return y