What should you pay attention to when a C++ function returns a generic type?

When returning a generic type in C, you need to declare the return type and use the template keyword. Constrain type parameters to ensure compliance with specific requirements and can return a generic container. Use generics with caution, especially when involving arithmetic operations.

C Precautions when a function returns a generic type

When writing code in C, when a function returns a generic type Extra caution is required. The following are a few key points to note:

1. Declare the return type of the function

When declaring a function that returns a generic type, use template keyword and specify type parameters. For example:

template<typename T>
T max(T a, T b) {
  return (a > b) ? a : b;
}

2. Constraint type parameters

You can use class or typename constraint type parameters. For example:

template<class T>
requires std::is_arithmetic<T>::value
T sum(T a, T b) {
  return a + b;
}

3. Return a generic container

You can return a generic container, such as std::vector or std ::map. For example:

template<typename T>
std::vector<T> createVector(int size) {
  return std::vector<T>(size);
}

Practical case: Function that sums two generic types based on value

template<typename T, typename U>
auto sum(T a, U b) {
  return static_cast<decltype(a + b)>(a) + static_cast<decltype(a + b)>(b);
}

int main() {
  int x = 5;
  double y = 3.14;
  std::cout << sum(x, y) << std::endl; // 输出：8.14
}

Summary of key points:

• Declare the return type of the function and use the template keyword.
• Constrain type parameters to ensure they meet specific requirements.
• Can return a generic container.
• Use generics with caution, especially when arithmetic operations are involved.

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