How to use functions in C++?

Using Functions in C A function is a reusable block of code used to increase code reusability and modularity. A function declaration specifies the function name, parameter types, and return type. The function definition provides the implementation of the function body. A function is called by using its name and passing the appropriate parameters.

Using functions in C

A function is a block of code that can be used repeatedly in a program. It can improve the code reusability and modularity. In C, the syntax of a function is as follows:

return_type function_name(parameter_list) {
    // 函数体
}

where:

• return_type is the type of value returned by the function. void if the function returns no value.
• function_name is the name of the function.
• parameter_list is the parameter list of the function, used to pass parameters to the function.

Function declaration and definition

Functions must be declared before they can be used. The function declaration specifies the name, parameter type and return type of the function. The syntax is as follows:

return_type function_name(parameter_list);

The function definition provides the implementation of the function body. The syntax is as follows:

return_type function_name(parameter_list) {
    // 函数体
}

Function call

To call a function, just use its name and pass the appropriate parameters, for example:

int sum(int a, int b) {
    return a + b;
}

int main() {
    int result = sum(10, 20);  // 调用 sum() 函数
    return 0;
}

Practical case

Let Let's write a C function that calculates the greatest common divisor (GCD) of two numbers:

int gcd(int a, int b) {
    while (b != 0) {
        int temp = b;
        b = a % b;
        a = temp;
    }
    return a;
}

int main() {
    int x = 12, y = 18;
    int result = gcd(x, y);  // 调用 gcd() 函数
    cout << "GCD of " << x << " and " << y << " is: " << result << "\n";
    return 0;
}

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