What is the most basic Container type a language can have? Some people may answer vectors, others would go with hash tables, but in this post Iago Leal de Freitas is arguing in favor of functions. post 
Yes, functions. Even though they aren’t generally seem as a data structure per se, we will see that most containers are in fact a way to represent a function with a given storage layout. To illustrate this “Functions Are Containers” idea, let’s take a look at an application that tightly couples both concepts: Memoization.
Sequences are functions that do not forget
Now consider the datatype of infinite streams as in the previous "The Lazy Way to Solve Differential Equations" post : […]
For Trees, we index using a breadth-first approach.