Pointer values are not being added together.

Question

I am trying to find the average price and mileage for the vehicles in the code. I am using pointers to run the values through a function, however, the outputs of the functions are not correct.

#include <stdio.h>
#include <string.h>
#define SIZE 4

typedef struct {
    int year;
    char model[11];
} Model;

typedef struct {
    float price;
} Price;

typedef struct {
    int miles;
} Miles;

typedef struct {
    Model year, model;
    Price price;
    Miles miles;
    struct Car *next;
} Car;

float averagePrice(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car* ptr_car4);
int averageMiles(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car *ptr_car4);

int main(void) {

    Car f1, im, f2, g;
    int i, cnt, avgmile;
    float avgprice;

    f1.year.year = 56;
    strcpy(f1.model.model, "Ford");
    f1.price.price = 500.00;
    f1.miles.miles = 23000;
    im.year.year = 64;
    strcpy(im.model.model, "Impala");
    im.price.price = 1800.00;
    im.miles.miles = 12000;
    f2.year.year = 57;
    strcpy(f2.model.model, "Ford");
    f2.price.price = 1400.00;
    f2.miles.miles = 22000;
    g.year.year = 65;
    strcpy(g.model.model, "Galaxy");
    g.price.price = 2600.00;
    g.miles.miles = 48000;
    avgprice = averagePrice(&f1, &im, &f2, &g);
    avgmile = averageMiles(&f1, &im, &f2, &g);
    printf("The average price of the vehicle is: %d.\n", avgprice);
    printf("The average miles of the vehicle is: %d.\n", avgmile);


    getchar();
    return 0;
}

float averagePrice(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car *ptr_car4) {
    float total;

    total = ptr_car->price.price;
    total =+ ptr_car2->price.price;
    total =+ ptr_car3->price.price;
    total =+ ptr_car4->price.price;

    total = total / SIZE;

    return total;
}

int averageMiles(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car* ptr_car4) {
    float total;

    total = ptr_car->miles.miles;
    total =+ ptr_car2->miles.miles;
    total =+ ptr_car3->miles.miles;
    total =+ ptr_car4->miles.miles;

    total = total / SIZE;

    return total;
}

I know I can not add pointer directly together so I added them to a variable to store the value. However, it appears to not store the values. I get 0 for the value of avgprice and 12000 for the value of avgmiles.

Answer 1

You've made three mistakes here:

• You wrote =+ instead of +=, thus re-assigning the value each time instead of adding it.
• You're using the %d (decimal) printf specifier, instead of the float specifier : %f.
• You've declared avgmile as being an int, when it is in fact a float.

#include <stdio.h>
#include <string.h>
#define SIZE 4

typedef struct {
    int year;
    char model[11];
} Model;

typedef struct {
    float price;
} Price;

typedef struct {
    int miles;
} Miles;

typedef struct {
    Model year, model;
    Price price;
    Miles miles;
    struct Car *next;
} Car;

float averagePrice(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car* ptr_car4);
int averageMiles(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car *ptr_car4);

int main(void) {

    Car f1, im, f2, g;
    int i, cnt;
    float avgprice, avgmile;

    f1.year.year = 56;
    strcpy(f1.model.model, "Ford");
    f1.price.price = 500.00;
    f1.miles.miles = 23000;
    im.year.year = 64;
    strcpy(im.model.model, "Impala");
    im.price.price = 1800.00;
    im.miles.miles = 12000;
    f2.year.year = 57;
    strcpy(f2.model.model, "Ford");
    f2.price.price = 1400.00;
    f2.miles.miles = 22000;
    g.year.year = 65;
    strcpy(g.model.model, "Galaxy");
    g.price.price = 2600.00;
    g.miles.miles = 48000;
    avgprice = averagePrice(&f1, &im, &f2, &g);
    avgmile = averageMiles(&f1, &im, &f2, &g);
    printf("The average price of the vehicle is: %f.\n", avgprice);
    printf("The average miles of the vehicle is: %f.\n", avgmile);


    getchar();
    return 0;
}

float averagePrice(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car *ptr_car4) {
    float total;

    total = ptr_car->price.price;
    total += ptr_car2->price.price;
    total += ptr_car3->price.price;
    total += ptr_car4->price.price;

    total = total / SIZE;

    return total;
}

int averageMiles(Car *ptr_car, Car *ptr_car2, Car *ptr_car3, Car* ptr_car4) {
    float total;

    total = ptr_car->miles.miles;
    total += ptr_car2->miles.miles;
    total += ptr_car3->miles.miles;
    total += ptr_car4->miles.miles;

    total = total / SIZE;

    return total;
}