Detect if character is number and add delay time

[IgorZ]

Hello i made a program based on the tutorial on youtube. It's suppose to calculate the average between 3 numbers so i got some questions about that.

1. How to detect when a person enters a number not a character = letter or non-numeric sign. So if he enters non-number i want the program to return him to the place where he entered it and ask him to enter the number again.
2. The program works great and calculates the average. The only thing i want is to add a delay time cuz when my program calculates the average it exits instantly(after 0.5 secs or something) so the person may not see the average.

Code:

# include <iostream>
using namespace std;
 
int main()
{
 
 
    double n1 = 0.0;
    double n2 = 0.0;
    double n3 = 0.0;
    double average = 0.0;
 
    std:: cout << "This program will calculate the average of 3 numbers " << std::endl;
    cout << "Enter the first number: " << endl;
    cin >> n1;
    cout << "Enter the second number: " << endl;
    cin >> n2;
    cout << "Enter the third number: " << endl;
    cin >> n3;
 
    average = (n1 + n2 + n3) / 3;
 
    cout << "The average of the entered numbers is: " << average << endl << endl;
 
    system("PAUSE");
    return 0;
 
}

Thanks for replies

[weaknessforcats]

You might try an infinite while loop with an embedded switch statement:

while (1)
{
     Get a character
 
     switch (on that character)
     {
          case 0:
          case 1: 
          etc...
                 Call a function to do your work
                  break;
          case E:
          case e:
                  This is exit choice.
                  Do a return. If  this is in main(), this will stop the program.
          default:
                 Display invalid character message
                 break;
     }
}

There are any number of ways to do this. You might use this to display a menu and when a choice is made to do some work you could ask for your digit inside the function that was called using the menu choice.

[Banfa]

the header ctype.h contains a lot of useful functions for classifying characters. isdigit might be useful to you look it up in your standard library reference.

[donbock]

Looks like the OP wants to parse floating-point numbers. If so, then I'd suggest copying the input characters into a string and using strtod to parse the string.

If upon return, endptr points to a string of zero or more whitespace characters then the input string must have been a valid floating-point number.

However, I'm not sure what strtod does if it is passed a string containing only whitespace characters. You should try that as an experiment to see if you need to explicitly trap that case.

... or at least that's how I would do it in C. The OP is using C++; I leave it to the C++ gurus to reveal some fancy polymorphic overloaded magical better way to do it.

[IgorZ]

Can you give the full code of it? Because i'm only a begginer i don't understand it clearly...

[weaknessforcats]

I just did. The rules prevent me from giving you a complete solution that compiles and links. Just follow the directions in my post.

Also, use Google. There are all sorts of example code out there.