Software terminology

Acronyms

RAII: Resource Acquisition Is Initialisation -- std::unique_ptr, std::vector
RDID: Resource Destruction is Deletion
RTTI: Run Time Type Inspection, e.g., dynamic_cast<>
RVO: return value optimisation
SFINAE: substitution failure is not an error -- "Prune functions that do not yield valid template instantiations from a set of overloaded functions."
SDLC: software design lifecycle
ODR: one definition rule
CRTP: Curiously Recurring Template Pattern
ADL: Argument-dependent lookup, (Koenig lookup) cout(std::endl)
IIFE: immediately invoked function expression (lambda)
RPC: remote procedure call
SOA: Service Oriented Architectur
CQS: Command–query separation (CQS) is a principle of imperative computer programming. It was devised by Bertrand Meyer as part of his pioneering work on the Eiffel programming language. It states that every method should either be a command that performs an action, or a query that returns data to the caller, but not both. In other words, Asking a question should not change the answer.
CQRS: Command Query Responsibility Segregation. It's a pattern that I first heard described by Greg Young. At its heart is the notion that you can use a different model to update information than the model you use to read information. For some situations, this separation can be valuable, but be aware that for most systems CQRS adds risky complexity.

Black box testing: examines the functionality of an application without peering into its internal structures or workings.
White box testing: tests internal structures or workings of an application
Unit, integration and system level testing

If you can detect a function has been run then it's not pure.

Caching the results of expensive functions
On first call of function store the results, if the function is called again with the same input then just return the cache