How to put function inside structure? [C]

[akif13]

Hello guys. My question is on the title. This is just an exercise that I wanted to do before my final exam. It's quite hard for me to understand. I hope you can give me good explanation or any examples that are related to this question. Sorry for any grammatical errors. English is my 2nd language.

Question:
EXERCISE 1
 Create a structure called Car. The members are brand and price.
In main( ) :
 Create a structure array called C of size 5
 Call function get_input(...), passing in array C
 Call function display(....),p assing in array C
In function get_input(...) :
 Get user input for brand and price.
In function display(....) :
 Displaying all car records whose price is more than 80K

Sample output screen
Enter car brand : Honda
Enter car price : RM 79000.00
Enter car brand : Toyota
Enter car price : RM 108000.00
Enter car brand : BMW
Enter car price : RM 390800.00
Enter car brand : Kelisa
Enter car price : RM 32000.00
Enter car brand : Myvi
Enter car price : RM 45900.00
Car brand : Toyota
Car price : RM 108000.00
Car brand : BMW
Car price : RM 390800.00

My coding:

#include <stdio.h>

struct CAR
{
    char brand[20];
    float price;
    float get_input(char brand, float price, int i);
    float display(char brand, float price, int i);
};

int main()
{
    struct CAR C[5]
    {
        float get_input(char brand, float price, int i);
        float display(char brand, float price, int i);
    }

    float get_input(char brand, float price, int i)
    {
        for(i = 0; i < 5; i++))
        {
        printf("Enter car brand : ");
        scanf("%s", C[i].brand);
        printf("\nEnter car price : RM ");
        scanf("%f", &C[i].price);
        }
    }
    float display(char brand, float price, int i)
    {
        if (C[i].price > 80000)
        printf("\nCar brand : %s", C[i].brand);
        printf("\nCar price : RM %.2f", C[i].price);
        else
        printf("\n");
    }
    }

Errors:
Line 7: field 'get_input' declared as a function
line 8: filed 'display' declared as a function
line 9: warning: useless storage class specifier in empty declaration In function 'main':
line 14: expected '=', ',', ';', 'asm' or '_attribute_' before '{' token In function 'get_input':
line 21: expected statement before ')' token
line 24: 'C' undeclared (first use in this function)
line 24: (Each undeclared identifier is reported only once In function 'display'
line 31: 'C' undeclared (first use in this function)
line 34: 'else' without a previous 'if'

[weaknessforcats]

In C you cannot put a function inside a struct. You can only put types or pointers to types inside the struct.

This function prototype:

float get_input(char brand, float price, int i);

needs to be in the struct as a function pointer. In this case it would be a pointer to a function that takes char, float and int arguments and returns a float. Like this:

float (*get_input)(char brand, float price, int i);

You would then assign the address of whatever function you want as long as that function has the same three arguments an returns a float.

[akif13]

I already fixed it. But when I compile it, it shows nothing. Quite confused here.

#include <stdio.h>

struct CAR
{
    char brand[20];
    float price;
    float (*get_input)(char brand, float price, int i);
    int (*display)(char brand, float price, int i);
};

int main()
{
    struct CAR C[5];

    float get_input(char brand, float price, int i)
    {
        for (i = 0; i < 5; i++)
        {
        printf("Enter car brand : ");
        scanf("%s", C[i].brand);
        printf("\nEnter car price : RM ");
        scanf("%f", &C[i].price);
        }
    }
    int display(char brand, float price, int i)
    {
        if (C[i].price > 80000)
        {
        printf("\nCar brand : %s", C[i].brand);
        printf("\nCar price : RM %.2f", C[i].price);
        }
        else
        printf("\n");
    }
    }

[weaknessforcats]

Firstly, you have functions defined inside main(). Functions cannot be defined inside other functions.
Second, you need to create a Car varable and then assign the address of your function to the function pointer in the variable. Then you can call the function using the variable:

struct Data
{
void (*display)();
};

void MyDisplay()
{
printf("Hello world!\n");
}
int main()
{
struct Data var;
var.display = MyDisplay;
var.display(); /* function call. you see Hello world! */

[donbock]

The problem statement does not direct you to include any functions or function pointers in the structure. It only says that you must provide a structure with two members (brand and price); and provide two functions (get_input() and display()). It goes on to require that those functions must take an entire structure array as one of their parameters. Your get_input() and display() functions do not meet that requirement.

[weaknessforcats]

Good point. I missed that. Too much C++, I guess.