m05-type-driven

Strong types prevent mixing different integer IDs like UserId and OrderId in C++ by wrapping primitive values in distinct structs. This type-driven design encodes domain boundaries directly into the type system, catching accidental misuse at compile time before runtime bugs occur.

Phantom types in C++ are template parameters used to encode metadata without adding runtime storage. They allow the type system to track state or domain distinctions, ensuring that only valid operations compile while keeping the generated code zero-cost.

You can enforce valid state transitions at compile time in C++ using the type-state pattern and builder patterns. By encoding states as distinct types, the compiler restricts invalid sequences, ensuring resources or file operations follow valid construction steps.

Type-driven design does not require external libraries for C++ APIs. It relies entirely on native templates and type design to achieve compile-time guarantees, meaning you can enforce safety for domain models and resource handles with zero external runtime dependencies.

The best way to protect floating point monetary values from bugs in C++ is applying strong types. Wrapping doubles in dedicated structs prevents accidental domain mixing and arithmetic errors, enforcing API safety through template-driven compile-time checks.

You should avoid type-state patterns in C++ design when state transitions are highly dynamic or determined at runtime. Because type-state relies on compile-time template enforcement, runtime-dependent states cannot be fully validated by the type system and require alternative logic.