FAQ about C++ function return values: types and meanings

C The function return value type can be any valid data type, including built-in types, user-defined types or void. If not explicitly specified, the return type is int. The void function does not return any value, but it can modify the program state. Local variables cannot be returned, but their data location can be returned using a pointer or reference. Standard C does not support returning multiple values ​​directly, but it can be achieved through structure, reference or pointer parameters.

FAQ about C function return values: Types and meaning

In C, the function return value is when the function is defined The specified data type. It represents the value returned to the caller when the function is executed. Although this is a simple concept, there are several issues that often plague developers.

1. Can the return type be any data type?

Yes, the return type can be any valid C data type, including built-in types (such as int, float, bool, etc.), user-defined types (such as structures, classes), and even void.

2. What if the function does not explicitly specify the return value type?

You can explicitly return the return value of a function through the return statement. If not explicitly specified, the function's return type is int and returns the value assigned to it at the point of call.

3. What is a void function?

void function is a function that does not return any value. They are typically used to perform operations that modify the state of the program, such as printing output or updating variables.

4. Can local variables be returned?

No, functions cannot return local variables. Local variables will be destroyed after they go out of function scope. Instead, you can use a pointer or reference to return the data location pointed to by a local variable.

5. How to return multiple values?

Standard C does not provide a method to directly return multiple values. Common solutions are to use a structure or class to encapsulate multiple values, or to modify caller-supplied variables via reference or pointer parameters.

Practical case:

The following code shows how to define functions of various return types:

// 返回整型的函数
int add(int a, int b) {
  return a + b;
}

// 返回浮点型的函数
float divide(float a, float b) {
  return a / b;
}

// 返回结构的函数
struct Point {
  int x;
  int y;
};

Point createPoint(int x, int y) {
  return Point{x, y};
}

// void 函数
void printMessage(const char* message) {
  std::cout << message << std::endl;
}

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