How do C++ functions handle multiple return values?

C functions can return multiple values ​​in three ways: Using a structure: Create a structure and use it as a return value, use the dot operator to access the structure members. Working with tuples: Use std::tuple to create a tuple and std::get<N>(tuple) to get the value in the tuple. Pass multiple parameters: Pass function parameters as references and return values ​​as output parameters.

#Returning multiple values ​​from a C function

In C programming, functions usually return a single value. But sometimes, you need to return multiple values ​​from a function. This can be achieved by using structures, tuples or specifying multiple parameters.

Use a structure to return multiple values

A structure is an aggregate type that can be used to store multiple values. You can create your own struct type and return it as a function value. For example:

struct Point {
    int x;
    int y;
};

Point getCoordinates() {
    // 计算 x 和 y 值
    return {5, 10};
}

This function returns a structure of type Point containing the x and y coordinates. You can access structure members using the dot operator (.).

Use tuples to return multiple values

A tuple is a lightweight container that can store different types of values. You can use the std::tuple class to create tuples. For example:

std::tuple<int, int> getCoordinates() {
    // 计算 x 和 y 值
    return std::make_tuple(5, 10);
}

This function returns a tuple of type std::tuple<int, int> containing the x and y coordinates. You can use std::get<N>(tuple) to get the value at a specific index in the tuple.

Returning multiple values ​​via multiple parameters

You can also return multiple values ​​by specifying multiple function parameters. For example:

void getCoordinates(int& x, int& y) {
    // 计算 x 和 y 值
    x = 5;
    y = 10;
}

This function returns the x and y coordinates as output parameters by passing the x and y parameters as references.

Practical case

The following is a practical case of using a tuple to return multiple values:

Suppose we have a method that obtains the length and width of a rectangle function. We can return these two values ​​using a tuple as shown below:

#include <tuple>

std::tuple<int, int> getRectangleDimensions() {
    // 获取矩形的长和宽
    int length = 5;
    int width = 10;

    // 返回一个包含长和宽的元组
    return std::make_tuple(length, width);
}

Now we can access the length and width of the rectangle using a tuple:

auto dimensions = getRectangleDimensions();
int length = std::get<0>(dimensions);
int width = std::get<1>(dimensions);

Output:

length: 5
width: 10

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