What are the key points to note when using C++ function templates?

C Notes on using function templates: Explicitly specify the template parameter type. Take advantage of type inference capabilities. Use template specializations to handle specific types. Set default type parameters. Pay attention to non-template function overload priority.

Precautions for using C function templates

When using C function templates, you need to pay attention to the following points:

1. Explicit template parameter type specification

When the template parameter type is omitted in the function declaration, the compiler will try to infer the type from the function call. However, this may cause compiler errors or unexpected behavior. Therefore, it is recommended to always specify template parameter types explicitly. For example:

template <typename T>
void foo(T x) {
  // ...
}

2. Type deduction

C 11 introduces the type deduction function, allowing template parameter types to be deduced from function parameters. If the function has only one template parameter, you can use the auto keyword for type deduction:

template <typename T>
void foo(auto x) {
  // ...
}

3. Specialize

when the template function Template specializations can be used when behavior needs to be different for certain types. Specialization is achieved by declaring a separate function implementation for a specific type:

template <typename T>
void foo(T x) {
  // 默认实现
}

template <>
void foo(int x) {
  // 特化实现
}

4. Default type parameters

Default type parameters allow default template parameters to be specified in the function declaration type. This allows the caller to use the function without explicitly specifying the type parameter:

template <typename T = int>
void foo(T x) {
  // ...
}

5. Non-template function overloading

If the function template is different from the non-template If the signatures of the functions are the same, non-template functions will be matched first. To avoid this, you can use the enable_if or SFINAE (a false-true name in an expression) technique.

Practical Case

The following is an example of using a function template to calculate the sum of elements of any type of array:

template <typename T>
T sum_array(T arr[], int size) {
  T sum = 0;
  for (int i = 0; i < size; ++i) {
    sum += arr[i];
  }
  return sum;
}

int main() {
  int arr[] = {1, 2, 3, 4, 5};
  double arr2[] = {1.2, 2.3, 3.4, 4.5, 5.6};
  std::cout << sum_array(arr, 5) << std::endl; // 输出：15
  std::cout << sum_array(arr2, 5) << std::endl; // 输出：17
  return 0;
}

The above is the detailed content of What are the key points to note when using C++ function templates?. For more information, please follow other related articles on the PHP Chinese website!