IsNumeric equivalent in C++

[atacess]

		//Prompting user for numbers
		cout << "Please input two numbers" << endl;
		cin >> num1;
		cin >> num2;

I am developing a simple C++ calculator for practice. Is there an IsNumeric (from VB) equivalent in C++ where I can prevent user from crashing the program by entering non-numerical inputs? Thank you in advance!

[ciphermagi]

You could try if (cin.bad()) or if (cin.fail())
I'm not sure off the top of my head whether that would be sufficient error checking, but it's worth a shot.

[gelatine]

use stringstream;small example here.

#include <iostream>
#include <string>
#include <sstream>
using namespace std;

int main ()
{
  string mystr;
  float price=0;
  int quantity=0;

  cout << "Enter price: ";
  getline (cin,mystr);
  stringstream(mystr) >> price;
  cout << "Enter quantity: ";
  getline (cin,mystr);
  stringstream(mystr) >> quantity;
  cout << "Total price: " << price*quantity << endl;
  return 0;
}

[atacess]

#include <iostream>
#include "conio.h"
#include <string>
#include <sstream>
using namespace std;
double add(int x, int y);
double subtract(int x, int y);


int main(){
	bool restartBoo = true;
		while(restartBoo)
		{
		//Variables declaration
		string userInput;
		int num1;
		int num2;
		char type;
		char restartChar;
		bool userChar = true;

		//Prompting the user on calculation type and storing numbers
		cout << "What do you want to do, enter a for addition or s for subtraction?" << endl;
		cin >> type;

		//Validating calculation type
		while(userChar)
		{
			if(type == 'a' || type == 's')
			{userChar = false;}

			else
			{
			userChar = true;
			cout << "You have entered an invalid character, a or s in lower case only, please re-enter." << endl;
			cin >> type;
			}
		} 

		//Prompting user for numbers
		cout << "You have chosen " << type << endl;

		cout << "Please input the first number" << endl;
		getline (cin, userInput);
		stringstream(userInput) >> num1;

		cout << "Please input the second number" << endl;
		getline (cin, userInput);
		stringstream(userInput) >> num2;

		//Code for different calculation cases
		switch (type)
		{
			case 'a':
				cout << add(num1, num2) << endl;
				break;

			case 's':
				cout << subtract(num1, num2) << endl;
				break;

			default:
				cout << "You have entered an invalid calculation type, type a or s only." << endl;
				break;
		}

		//Prompting the user for restart
		cout << "Do you want to start over? y/n" << endl;
		cin >> restartChar;
		
		//Code for restart cases
		if(restartChar == 'y')
			{
			restartBoo = true;
			system("cls"); 
			}

		else if(restartChar == 'n')
			{restartBoo = false;}

		else
			{
			cout << "You have entered an invalid character!" << endl;
			restartBoo = true;
			}
		
		}

    _getch();
	return 0;
	
}

double add(int x, int y){
	return x + y;
}

double subtract(int x, int y){
	return x - y;
}

This is the code for very first C++ addition/subtraction calculator. I tried stringstream as suggested but I did not get the desired result as the user gets prompted at the same time for inputting the first and second number. I do not know what went wrong, any help will be appreciated, thank you!

[ciphermagi]

If it's simply that the user is getting prompted to re-enter the first and second number, then you should exclude the user getting prompted from the loop that tests for correct input from the addition/subtraction tree.

[Stewbond]

The stringstream method you used, isn't different at all from using cin. Here you're just copying one stream to another.

Use something like this instead:

int a;
do
{
  cin.clear();
  cin >> a;
} while (cin.fail());

Or maybe:

int a;
while (cin.peek() < '0' || cin.peek() > '9')
{
  cin >> a;
}

[atacess]

I refer to line 41 - 49 specifically.

I got "Please input the first number" and "Please input the second number" displayed simultaneously but I want the former to appear first followed by the latter. I have no idea how to fix it.

I had tried the small example given by gelatine and it works well. I do not know why mine does not work as expected.