CPP Templates & Generic Programming 2

Question 1

What is the purpose of `std::enable_if` in template programming?

Accepted Answer

To conditionally enable a template specialization based on a compile-time boolean

Answer

`std::enable_if` uses SFINAE to include or exclude a template overload based on a compile-time boolean condition.

Question 2

Which of the following correctly declares a variadic template function?

Accepted Answer

template<typename... Args> void f(Args... args);

Answer

The `...` after `typename` declares a parameter pack, and `Args... args` expands it in the function parameter list.

Question 3

What does `sizeof...(Args)` return in a variadic template?

Accepted Answer

The number of types in the parameter pack

Answer

`sizeof...(Args)` is a compile-time operator that returns the number of elements in a parameter pack.

Question 4

Which concept best describes SFINAE?

Accepted Answer

Substitution Failure Is Not An Error — invalid template substitutions are silently discarded

Answer

SFINAE means that when template argument substitution fails, the compiler removes that overload from consideration instead of issuing an error.

Question 5

What is a 'fold expression' introduced in C++17 for variadic templates?

Accepted Answer

A compact syntax to apply a binary operator to all elements of a parameter pack

Answer

Fold expressions allow applying operators like `+` or `&&` across all pack elements, e.g., `(args + ...)` sums the pack.

(CPP) C++ Programming Professional Certificate Practice Test