import legrandchien as lgc

if __name__ == "__main__":
    g = lgc.Const(-10)
    m = lgc.Const(1)

    x = lgc.Var("x")

    T = 0.5 * m * x.diff() * x.diff()
    V = m * g * x
    L = T - V

    dL = L.diff()

    dico = {
        "x" : 0,
        "d_x" : 1,
        "d_d_x" : 1,
    }

    print(dL.evaluate(dico))