The relationship between C++ function parameter passing methods and template metaprogramming

The relationship between the function parameter passing method and template metaprogramming: value passing: copying the parameter value, the function cannot modify the original variable. Pass by reference: Pass a reference to the parameter, and the function can modify the original variable. Pointer passing: passing a pointer to a parameter, the function can modify the original variable by dereferencing the pointer. Template metaprogramming can generate different codes based on parameter types by specifying the parameter passing method.

The relationship between function parameter passing method and template metaprogramming

In C, function parameters can pass values There are three ways of passing , reference passing and pointer passing. Template metaprogramming (TMP) is a powerful and flexible technique that allows you to generate code using compile-time information. There is a close connection between parameter passing methods and TMP.

Value passing

Value passing copies the value of a function parameter and passes it to the function. The function cannot modify the original variable because it no longer references the variable. This is the simplest and most common delivery method.

void printNumber(int n) {
  std::cout << n << std::endl;
}

int main() {
  int a = 10;
  printNumber(a);  // 值传递
  return 0;
}

Pass by reference

Pass by reference passes a reference to the function parameter to the function. The function can modify the original variable because it references it. Passing by reference is more efficient than passing by value, especially when passing large objects.

void swap(int& a, int& b) {
  int temp = a;
  a = b;
  b = temp;
}

int main() {
  int a = 10, b = 20;
  swap(a, b);  // 引用传递
  std::cout << a << " " << b << std::endl;  // 输出：20 10
  return 0;
}

Pointer passing

Pointer passing passes pointers to function parameters to a function. Functions can modify the original variable by dereferencing the pointer. Passing by pointer is more flexible than passing by reference, but also introduces more indirection.

void printArray(int* arr, int size) {
  for (int i = 0; i < size; i++) {
    std::cout << arr[i] << " ";
  }
  std::cout << std::endl;
}

int main() {
  int arr[] = {1, 2, 3, 4, 5};
  printArray(arr, 5);  // 指针传递
  return 0;
}

Template Metaprogramming

TMP allows you to generate code using compile-time information. The parameter passing method can be specified through TMP, thereby generating different codes for different types of parameters.

template <typename T>
void printValue(T value) {
  // 根据 T 的类型打印 value
  if constexpr (std::is_integral<T>::value) {
    std::cout << "整型：";
  } else if constexpr (std::is_floating_point<T>::value) {
    std::cout << "浮点型：";
  }
  std::cout << value << std::endl;
}

int main() {
  printValue(10);  // 整型：10
  printValue(3.14);  // 浮点型：3.14
  return 0;
}

These are just a few examples of the connection between how C function arguments are passed and TMP. Understanding these concepts can help you write more flexible and efficient code.

The above is the detailed content of The relationship between C++ function parameter passing methods and template metaprogramming. For more information, please follow other related articles on the PHP Chinese website!