"""Example from the exercise 03 sept 2026: Write a function 
that uses a forward difference to compute the derivative
of a function f(x) in a point x. The function f and the 
point x are given as arguments."""



def diff(f, x, h=1e-6):
    r = (f(x + h) - f(x)) / h
    return r


def g(x):
    return x**2 - 2

x = 2.0
dg = diff(g, x=x)
print(f"dg/dx = {dg:g}")

"""
Alternatively, we can use a lambda function to specify the
function directly in the argument list to diff:"""

dg = diff(lambda x: x**3 - 4*x + 2, x=1.5)
print(f"dg/dx = {dg:g}")

"""
Terminal> python num_diff.py 
dg/dx = 4
dg/dx = 2.75
"""