A self-contained C/C++ rational number engine used by the calculator's core. It implements custom arbitrary-precision NUMBER and RAT types, base conversion, transcendentals, and rational arithmetic without requiring the rest of the app. This is highly reusable for any project needing exact, high-precision mathematical computation.

Centralizes clipboard parsing and validation for all calculator modes, enforcing per-mode syntax rules, radix constraints, operand sanitization, and length limits. The pattern of separating paste validation from UI logic is directly reusable in any application that accepts externally supplied numeric or expression input.

A self-contained C# page-object framework for driving UWP applications via WinAppDriver. It abstracts calculator panels, results, history, memory, and navigation into composable test components and includes helper extensions for window management and element interaction. This can be extracted and adapted for UI automation of other Windows desktop apps.

Implements keyboard shortcut registration as a XAML attached property, with per-window state and weak-reference event handling to avoid leaks. This is a clean, reusable pattern for any XAML application needing declarative, localized keyboard shortcut bindings.