Verry new at programing.

OK I just started my very first C++ class and I am working on a lab. Here is the code I wrote and a break down of what I'm trying to do.

My code is doing what I want it to do. However what I am trying to figure out is if the users enters in anything other then a number I want it to spit out an error that say's "invalid input"

I've tried doing it with an else statemnt but can't get it it to work. Here is my code.

Code:

---

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    //declare variables
    int Temp1 = 0;
    int Temp2 = 0;
    int AverageTemp = 0;
   
    cout << "Follow the steps to find the average temp between two cities." <<endl;
    cout <<endl;
    cout << "Enter temp for 1st city: ";
    cin >> Temp1;
    cout << "Enter temp for 2nd city: ";
    cin >> Temp2;
 
   
      if(Temp1 >= 120)
{
    cout << "Error Temp1 is WAY TO HOT! Temp can not exceed or be equal to 120." <<endl;
    cout << "Please re-enter temp for 1st city: ";
    cin >> Temp1;
    }
   
    if(Temp2 >= 120)
{
    cout << "Error Temp2 is WAY TO HOT! Temp can not exceed or be equal to 120." <<endl;
    cout << "Please re-enter temp for 2nd city: ";
    cin >> Temp2;
   
    }
    if (Temp1 < 120 || Temp2 < 120)
   
{
    AverageTemp = (Temp1 + Temp2) / 2;
    cout << "Average temp: " << AverageTemp <<endl;
        }

    if (Temp1 > Temp2)
    cout <<"City 1 is warmer then city 2." <<endl;
    if (Temp1 < Temp2)
    cout <<"City 2 is warmer then City 1." <<endl;
    if (Temp1 == Temp2)
    cout <<"Both temps are equal." <<endl;
   
   



   
    system("pause");
    return 0;
   
   
}

---

Thanks in advance.

It ain't rocket science.

Code:

---

if (such-and-such-is-true)
{
  // Do code in this block
}
else
{
  // Do code in this block
}

---

Thank you for your response.

I'm having a hard time wraping my head around how to tell it to say "invalid input" for anything other then a number.

There are several ways. My favorite is:

Code:

---

std::string input;
std::getline(input, std::cin);
int x;
try
{
    x = boost::lexical_cast<int>(input);
}
catch(boost::bad_lexical_cast&)
{
    // User entered bad input
}

---

It isn't the easiest thing to do this, and this example assumes you are somewhat familiar with calling template functions (you may have used such syntax in std::vector<T>, for example) and exceptions.

With all due respect to Elysia, perhaps if you describe your help as not very useful without a deeper understanding of a moderately advanced subject in C++ programming, perhaps it is unwise advice to give to a beginner. Also, be careful using RTTI. It can often be avoided.

To gec5741, you may also wish to investigate switch statements.

As I said, it is not the most trivial task.
It is my favorite solutions - and there are others, but they may involve complexity, as well. In their own way.

Another solution might be:

Code:

---

int x;
if (!(std::cin >> x))
{
    std::cin.clear();
    std::cin.ignore(std::numeric_limits<int>::max());
    // User entered bad input
}

---

Not sure if this is 100% correct.

Thank you for your suggestions. I am as I said a begginer so what you suggest may be a bit advanced for this project. It's my second lab in this class ;)

I will look into using a switch statements.

thanks.

Quote:

---

Originally Posted by sphynxter

Also, be careful using RTTI. It can often be avoided.

---

Yes, but where is RTTI used? :|

Quote:

---

Originally Posted by Elysia

Not sure if this is 100% correct.

---

I think cin.clear() should come before the cin.ignore().

EDIT:

Quote:

---

Originally Posted by gec5741

I will look into using a switch statements.

---

I do not think that switch statements are an appropriate solution to the problem of checking if the user entered invalid input that is not a number. Elysia's first suggestion requires a useful but non-standard library, and the second suggestion uses only the standard library and is on the right track.

You also may want to improve on your indentation.

Im unlcear on what the rules for indentations are really?

Is this any better?

Code:

---

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char *argv[])
{
    //declare variables
    int Temp1 = 0;
    int Temp2 = 0;
    int AverageTemp = 0;
   
   
    cout << "Follow the steps to find the average temp between two cities." <<endl;
    cout <<endl;
    cout << "Enter temp for 1st city: ";
    cin >> Temp1;
    cout << "Enter temp for 2nd city: ";
    cin >> Temp2;
 
   
    if(Temp1 >= 120)
{
    cout << "Error Temp1 is WAY TO HOT! Temp can not exceed or be equal to 120." <<endl;
    cout << "Please re-enter temp for 1st city: ";
    cin >> Temp1;
    }
   
    if(Temp2 >= 120)
{
    cout << "Error Temp2 is WAY TO HOT! Temp can not exceed or be equal to 120." <<endl;
    cout << "Please re-enter temp for 2nd city: ";
    cin >> Temp2;
    }
    else
{
    AverageTemp = (Temp1 + Temp2) / 2;
    cout << "Average temp: " << AverageTemp <<endl;
        }

    if (Temp1 > Temp2)
    cout <<"City 1 is warmer then city 2." <<endl;
    if (Temp1 < Temp2)
    cout <<"City 2 is warmer then City 1." <<endl;
    if (Temp1 == Temp2)
    cout <<"Both temps are equal." <<endl;
   
   



   
    system("pause");
    return 0;
   
   
}

---

An example:

Code:

---

#include <cstdlib>
#include <iostream>

using namespace std;

int main(int argc, char* argv[])
{
    //declare variables
    int Temp1 = 0;
    int Temp2 = 0;
    int AverageTemp = 0;

    cout << "Follow the steps to find the average temp between two cities." << endl;
    cout << endl;
    cout << "Enter temp for 1st city: ";
    cin >> Temp1;
    cout << "Enter temp for 2nd city: ";
    cin >> Temp2;

    if (Temp1 >= 120)
    {
        cout << "Error Temp1 is WAY TO HOT! Temp can not exceed or be equal to 120." << endl;
        cout << "Please re-enter temp for 1st city: ";
        cin >> Temp1;
    }

    if (Temp2 >= 120)
    {
        cout << "Error Temp2 is WAY TO HOT! Temp can not exceed or be equal to 120." << endl;
        cout << "Please re-enter temp for 2nd city: ";
        cin >> Temp2;
    }
    else
    {
        AverageTemp = (Temp1 + Temp2) / 2;
        cout << "Average temp: " << AverageTemp << endl;
    }

    if (Temp1 > Temp2)
        cout << "City 1 is warmer then city 2." << endl;
    if (Temp1 < Temp2)
        cout << "City 2 is warmer then City 1." << endl;
    if (Temp1 == Temp2)
        cout << "Both temps are equal." << endl;

    system("pause");
    return 0;
}

---