# Exercise 2.16

I think we should implement the concept of identity in order to solve this problem, our procedures should be able to expand the functions and solve it. It’s really hard to implement an interval-arithmetic package where parts can be used in bigger procedures. The best solution would be to only use procedures alone without building them from smaller procedures but then it’s against the essence of programming.\ This problem is far from trivial.

More reading here : https://en.wikipedia.org/wiki/Interval_arithmetic#Dependency_problem