Making sure only one data type is inputted

Hi, im new to c++ and im trying to better myself..

i am trying to make a simple calculator and wanted to be able to make sure the user only can enter a int at some points and double at others. I've tried a few different If statements however they haven't worked so far. Here's some of my code

Code:

int quad()
{
.. .. //local variables
.. .. double a,b,c,d,e,f,g;
.. .. 
.. .. char cLoop;








//function
.. .. do {cout << "This is the page for the quadratic formula (aX2+bX+c)";
.. .. cout << "\n Please enter a: ";
.. .. cin >> a;                                         //Want it to check here
.. .. cout << "\n Please enter b: ";
.. .. cin >> b;
.. .. cout << "\n Please enter c: ";
.. .. cin >> c;
.. .. d = pow(b,2) - 4 * a * c;
.. .. if (d < 0)
.. .. .. .. {
.. .. .. .. .. .. cout << "\nNo Real Roots!";
.. .. .. .. }
.. .. else if (d = 0)
.. .. .. .. {
.. .. .. .. .. .. cout << "One Real Root: ";
.. .. .. .. .. .. e = -b + ((sqrt(d)) / 2 * a);
.. .. .. .. .. .. cout << "\n Your Root Is" << e;
.. .. .. .. }
.. .. else
.. .. .. .. {
.. .. .. .. .. .. cout << "Your Roots Are: ";
.. .. .. .. .. .. f = -b + ((sqrt(d)) / 2 * a);
.. .. .. .. .. .. g = -b - ((sqrt(d)) / 2 * a);
.. .. .. .. .. .. cout << "\nX = " << f;
.. .. .. .. .. .. cout << "\nX = " << g;
.. .. .. .. }
.. .. .. .. cout << "Do you wish to do this again? Y or N.\n";
.. .. .. .. cin >> cLoop;




.. .. } while (cLoop == 'Y' || cLoop == 'y');




.. .. return 0;
}

thanks for any help.

You could read the entire line as a string

Code:

string line;
getline(cin, line);

and then see if it contains a decimal point or not.

What's with all the dots in your code listing? Try to get rid of them if you post more code.

Originally Posted by oogabooga

..
and then see if it contains a decimal point or not.
..

Do that with stringstreams, btw; not manually.

double number;
cin >> number;
(number == (int)number); //will be true if number is an int, otherwise it will be false.

That's too brittle. When an operation on cin fails, it will not change the operand.

Code:

#include <iostream>
using namespace std;

int main()
{
   double number = 0.0;
   cin >> number;
   if (number == int(number))
      cout << "good\n";
   else
      cout << "bad\n";
   return 0;
}

The suggestion only works if the number is not initialized.

The suggestion only works if the number is not initialized.

To be fair, you can check to see if the number has been modified:

Code:

if(cin >> number) // ...

Soma