Home page of personal blog (click to view details)-- https://blog.51cto.com/11495268
    

1, introduction

In C + + language, functions are needed for everything. This paper introduces the basic concepts related to functions, and understands their existence -- function definition, function call, function overload and function template (as for the special class functions in C + +, this article will not introduce them for the moment)
    

2. Function definition

//When defining a function, the parameters in parentheses after the function name are parameters
 Return value type function name ([parameter])
{
    Function body
}

3. Function call

// When a function is called, the parameters in parentheses after the function name are arguments
#include <iostream>
using namespace std;

void exchange_num(int *first_num, int *sec_num)
{
    int exchange_tmp = 0;
    exchange_tmp = *first_num;
    *first_num = *sec_num;
    *sec_num = exchange_tmp;
}

int main(void)
{
    int first_num = 1;
    int sec_num= 10;

    // Calling function
    exchange_num(&first_num, &sec_num);

    cout << "first_num:" << first_num << endl;
    cout << "sec_num:" << sec_num << endl; 

    return 0;
}

4. Function overload

C + + allows multiple functions to be defined by the same function name. Overloaded functions must have different parameter numbers or parameter types
    

// When a function is called, the parameters in parentheses after the function name are arguments
#include <iostream>
using namespace std;

void exchange_num(int *first_num, int *sec_num)
{
    int exchange_tmp = 0;
    exchange_tmp = *first_num;
    *first_num = *sec_num;
    *sec_num = exchange_tmp;
}

void exchange_num(double *first_num, double *sec_num)
{
    double exchange_tmp = 0;
    exchange_tmp = *first_num;
    *first_num = *sec_num;
    *sec_num = exchange_tmp;
}

int main(void)
{
    int ifirst_num = 1;
    int isec_num= 10;

    double dfirst_num = 1.1;
    double dsec_num = 10.01;

    // Calling function
    exchange_num(&ifirst_num, &isec_num);
    exchange_num(&dfirst_num, &dsec_num);

    cout << "ifirst_num:" << ifirst_num << endl;
    cout << "isec_num:" << isec_num << endl; 

    cout << "dfirst_num:" << dfirst_num << "\ndsec_num:" << dsec_num << endl; 

    return 0;
}

5. Function template

When overloading functions, it can be found that some overloaded functions are only of different parameter types. In C + + language, there are many data types, so it is not necessary to write an overloaded function for each type (theoretically, this is feasible), but it causes a lot of repeated code. Function template is just to solve this problem. It is recommended to use general functions when calling functions , the system will replace the virtual type in the template according to the type of arguments, so as to realize the functions of different functions

// When a function is called, the parameters in parentheses after the function name are arguments
// Template function call does not support implicit type conversion
#include <iostream>
using namespace std;

// The class keyword can also be replaced with the typename keyword
template <class c2>
void exchange_num(c2 *first_num, c2 *sec_num)
{
    c2 exchange_tmp = 0;
    exchange_tmp = *first_num;
    *first_num = *sec_num;
    *sec_num = exchange_tmp;
}
int main(void)
{
    int ifirst_num = 1;
    int isec_num= 10;

    double dfirst_num = 1.1;
    double dsec_num = 10.01;

    // Calling function
    exchange_num(&ifirst_num, &isec_num);
    exchange_num(&dfirst_num, &dsec_num);

    cout << "ifirst_num:" << ifirst_num << endl;
    cout << "isec_num:" << isec_num << endl; 

    cout << "dfirst_num:" << dfirst_num << "\ndsec_num:" << dsec_num << endl; 

    return 0;
}