Making sure only one data type is inputted

[Kinley Adams]

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

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.

[oogabooga]

You could read the entire line as a string

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.

[manasij7479]

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

Do that with stringstreams, btw; not manually.

[Dr_Regulus]

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

[whiteflags]

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

#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.

[phantomotap]

The suggestion only works if the number is not initialized.

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

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

Soma