Re^2: use Memoize;

[Corion]

Alternatively, instead of writing your own caching scheme, you could use a proven and documented approach, and use Memoize.

Also, the technical term for what you describe as "simply a mathematical function that is intended to return a result" is "pure function" or a subroutine without side-effects. Because, as the documentation of Memoize says, it will cache the results of a function for identical input values.