Templates & Generic Programming Flashcards

What is 'template metaprogramming' (TMP)?

Answer: Using templates to perform computations and generate code at compile time

TMP exploits the C++ template system as a Turing-complete compile-time computation engine, enabling zero-overhead abstractions.

Which C++20 feature provides a cleaner way to constrain template parameters than `enable_if`?

Answer: Concepts

C++20 Concepts allow attaching named semantic constraints directly to templates with `requires` clauses, replacing verbose `enable_if` idioms.

What is the `requires` keyword used for in C++20 template programming?

Answer: Specifying constraints that template arguments must satisfy

`requires` introduces a constraint on a template, and if the constraint is not satisfied the template is removed from overload resolution.

What is a 'policy-based design' in C++ generic programming?

Answer: Decomposing a class's behavior into interchangeable template parameters (policies)

Policy-based design (popularized by Andrei Alexandrescu) separates concerns into composable policy classes passed as template parameters.

What does `if constexpr` allow in template functions (C++17)?

Answer: Discarding branches at compile time based on a compile-time condition

`if constexpr` evaluates the condition at compile time and discards the false branch entirely, preventing instantiation of ill-formed code in that branch.

When a function template and a non-template function are equally viable overloads, which is preferred?

Answer: The non-template function is preferred

C++ overload resolution prefers non-template functions over equally-matched function template specializations.

What is 'template template parameters'?

Answer: A template parameter that itself is a class template, not a concrete type

Template template parameters accept a template (not a type) as an argument, e.g., `template class Container>` allows passing `std::vector` itself.