#!/usr/bin/python
import operator

def new_rap(x, func: str="0", der: str="0", iter=0):
    y_exper = func.replace("x", str(x)) 
    der_exper = der.replace("x", str(x))

    y = eval(y_exper)
    der = eval(der_exper)

    print(f"new_x = {x} - {y}/{der} [{iter}]")
    new_x = x - (y / der)
    return new_x

# def new_rap(x, func=nullfunc, dx=0.1):
#     new_x = None 
#     try:
#         while x != new_x:
#             y = func(x)
#             der = derive(x, func, dx)
#             new_x = x - y/der
#             if new_x == x:
#                 return new_x 
#             else:
#                 x = new_x
#         return x
#     except ZeroDivisionError as error:
#         print(f"{y=} {der=} {new_x=}")
#         print(error)

def eval_func( func: str, x: float ):
    y_exper = func.replace("x", str(x)) 
    return eval(y_exper)

def new_rap_method(x, funcstr: str="0", derstr: str="0", per=10):
    new_x = None
    i = 0
    while True:
        y = eval_func(funcstr, x)
        der = eval_func(derstr, x)

        print(f"new_x = {x} - {y}/{der} [{i}]")
        new_x = x - (y / der)
        i += 1

        if round(eval_func(funcstr, new_x), per) == 0:
            return round(new_x, per)
        else:
            x = new_x

if __name__ == "__main__":
    func = input("f(x) = ")
    der = input("f'(x) = ")
    randx = float(input("x = "))
    print("Doing newton-raphsons method to get root...")
    x = new_rap_method(randx, func, der)
    print(f"{x=}")