#!/usr/bin/python
# -*- coding: utf-8 -*-
import matplotlib.pyplot as plt
import numpy as np
import random
from math import *

delta = 0.1
minXY=-5.0
maxXY=5.0
nContour=50

def SampleFunc(x,y):
    return (x**2+y-11)**2

def ConstrainFunction(x):
    return (2.0*x+1.0)

def CreateMeshData():
    x = np.arange(minXY, maxXY, delta)
    y = np.arange(minXY, maxXY, delta)
    X, Y = np.meshgrid(x, y)
    Z=[SampleFunc(x,y) for (x,y) in zip(X,Y)]
    return(X,Y,Z)

# Main
start=np.matrix([random.uniform(minXY,maxXY),random.uniform(minXY,maxXY),0])

(X,Y,Z)=CreateMeshData()
CS = plt.contour(X, Y, Z,nContour)

Xc=np.arange(minXY,maxXY,delta)
Yc=[ConstrainFunction(x) for x in Xc]

#  plt.plot(start[0,0],start[0,1],"xr");
plt.plot(Xc,Yc,"-r");

# the answer from sympy
result=np.matrix([
[-1,-1],
[-1+sqrt(11),-1+2*sqrt(11)],
[-sqrt(11)-1,-2*sqrt(11)-1]])
print(result)

plt.plot(result[:,0],result[:,1],"or");

plt.axis([minXY, maxXY, minXY, maxXY])
plt.show()