Question

I am trying to write a program that tells the difference between the two times the user inputs. I am not sure how to go about this. I get the errors :

Line 27|error: invalid operands of types ‘int’ and ‘const MyTime*’ to binary ‘operator-‘|

Line |39|error: cannot convert ‘MyTime’ to ‘const MyTime*’ for argument ‘1’ to ‘int DetermineElapsedTime(const MyTime*, const MyTime*)’|

I also need a lot of help in this problem. I don’t have a good curriculum, and my class textbook is like cliffnotes for programming. This will be my last class at this university. The C++ teztbook I use(my own not for class) is Sam’s C++ One hour a day.

#include <iostream>
#include<cstdlib>
#include<cstring>

using namespace std;
struct MyTime { int hours, minutes, seconds; };
int DetermineElapsedTime(const MyTime *t1, const MyTime *t2);

long t1, t2;

int DetermineElapsedTime(const MyTime *t1, const MyTime *t2)
{
    return((int)t2-t1);
}


int main(void)
{
    char delim1, delim2;
    MyTime tm, tm2;
    cout << "Input two formats for the time. Separate each with a space. Ex: hr:min:sec\n";
    cin >> tm.hours >> delim1 >> tm.minutes >> delim2 >> tm.seconds;
    cin >> tm2.hours >> delim1 >> tm2.minutes >> delim2 >> tm2.seconds;

    DetermineElapsedTime(tm, tm2);

    return 0;

}

I have to fix the errors first. Anyone have any ideas??

Answer 1

Please take a look on your implementation of DetermineElapsedTime.

struct MyTime { int hours, minutes, seconds; };

...

int DetermineElapsedTime(const MyTime *t1, const MyTime *t2)
{
    return((int)t2-t1);
}

How the compiler should know what you mean with the line

    return((int)t2-t1);

You cannot simply subtract the two structures. You have to implement this by yourself.

EDIT:

Better you use

int DetermineElapsedTime(MyTime &t1, MyTime &t2)

this is more C++ like.

I end up with (still ugly, but for the moment only the main problem is remaining)

You still need to find a solution for the subtraction of your data in your MyTime structure.

#include <iostream>
#include<cstdlib>
#include<cstring>

using namespace std;
struct MyTime { int hours, minutes, seconds; };


int DetermineElapsedTime(MyTime &t1, MyTime &t2)
{
    // TODO: This is not correct! Implement the correct way.
    return((int)t2-t1);
}

int main(void)
{
    char delim1, delim2;
    MyTime tm, tm2;
    cout << "Input two formats for the time. Separate each with a space. Ex: hr:min:sec\n";
    cin >> tm.hours >> delim1 >> tm.minutes >> delim2 >> tm.seconds;
    cin >> tm2.hours >> delim1 >> tm2.minutes >> delim2 >> tm2.seconds;

    DetermineElapsedTime(tm, tm2);

    return 0;

}