"""
Ex. 5.11 from "A primer on..."
Modify the class from ex 6.1 with 
special methods __call__ and __str__.
"""

import numpy as np
from math import pi

class F:
    def __init__(self, a, w):
        self.a = a
        self.w = w

    def __call__(self, x):
        return np.exp(-self.a*x) * np.sin(self.w*x)
    
    def __str__(self):
        return f'exp(-{self.a}*x) * sin({self.w}*x)'

#usage:
f = F(a=1.0, w=0.1)
print(f(x=pi))  
print(f)     

"""
Terminal> python F2.py 
0.01335383513703555
exp(-1.0*x) * sin(0.1*x)
"""