Mix it in with open-high-low-close

Implementing mixins in C++ for extensible UI library design

This easy C++ coding problem tests your understanding of the Mixin pattern—a design technique that uses variadic templates and multiple inheritance to compose functionality without modifying base classes. It's popular in performance-sensitive domains like quantitative trading and game engines, where you need to extend types without breaking existing interfaces or creating explosion of derived classes.

The challenge here is to refactor an OHLC (open-high-low-close) market-data struct so that new fields like Label and Color can be mixed in at the library boundary, while keeping the original OHLC struct unchanged. You'll use a template base class that inherits from multiple mixin types, then redefine the public alias to point to the new composition. The key insight is inverting the usual inheritance tree: instead of deriving specialized OHLC types, you build OHLC as a template that pulls in extra functionality.

• Variadic templates and parameter packs
• Multiple inheritance and initialization
• Type aliases and public interfaces
• Separation of concerns via composition over modification