plf is a library that implements a piecewise-linear function (which is a real function of a real variable) and defines basic operation with it: addition, subtraction, multiplication, division, function composition, and taking definite integral.
It is used as an approximation of a continuous function (more precisely the density of a random variable) in the sample file fixpoint-nn.py, which tries to solve a functional equation for various parameters.
The demostration uses fixpoint-iteration method for solving the following functional problem.
Find real function 
such that:
python3 fixpoint-nn.py
python3python3-matplotlibpython3-numpy