C++ First program - Calculator - c++

Question

Hello I just started learning C++ and Im trying to make a calculator, right now having a fue problems that I simply dont know how to fix in C++.
#include <iostream>
using namespace std;
int main() {
int a, b, c, d;
cout << "1. Saskaitiissana(+)" << endl;
cout << "2. atnnemssana(-)" << endl;
cout << "3. daliissana(/)" << endl;
cout << "4. reizinaassana(*)" << endl;
cin >> d;
switch(d){
case 1 :
cout << "ievadiet a un b lai saskaitiitu(+)" << endl;
cin >> a;
cin >> b;
c = a + b;
cout << "The sum of number 1 and number 2 is " << c << "\n" <<endl;
break;
case 2 :
cout << "ievadiet a un b lai atnnemtu(-)" << endl;
cin >> a;
cin >> b;
c = a - b;
cout << c << endl;
break;
case 3 :
cout << "ievadiet a un b lai reizinaatu(*)" << endl;
cin >> a;
cin >> b;
c = a * b;
cout << c << endl;
break;
case 4 :
cout << "ievadiet a un b lai dal'itu(/)" << endl;
cin >> a;
cin >> b;
if(b==0)
{
cout<<"Nulle neder! start over."<<endl;
}
c = a/b;
cout << c << endl;
break;
}
return 0;
}
The things I still have to do.
Find the most easy way for the program to use numbers only. Also when I type in a number it can not be "empty space".
Also how can I make the case after it finish and gives you the result, go back to the begining of start menu? and if I want to exit a program I press esc or 5?
Also with the exit option I was thinking of useing do while "5" is pressed, can that work in c++?
Right now Im most interested on how to check program to use numbers only and have no empty space when adding numbers.
Thank you for your time :)

Answer 1

For ignoring non-numeric input you can this piece of code:
std::cin >> d;
while(std::cin.fail())
{
std::cin.clear();
std::cin.ignore(std::numeric_limits<std::streamsize>::max(),'\n');
std::cout << "Bad entry. Enter a NUMBER: ";
std::cin >> d;
}
or in C-style:
while(scanf("%i",&d)!=1)
{
fseek(stdin,0,SEEK_END);
}
You can also put your whole bunch of code in a while statement to re-run the calculator after one operation.

Answer 2

Taking into account the safe input:
//----------------------------------------------------------------------------
#include <iostream>
using namespace std;
//----------------------------------------------------------------------------
void SafeDouble (double &d)
{
while (!(cin >> d))
{ cin.clear();
while (cin.get() != '\n');
cout << "\tIncorrect. Try again\n\t";
}
cin.sync();
}
//----------------------------------------------------------------------------
int main()
{
cout << "The simpliest calculator\n";
double a = 0.,b = 0.;
cout << "\na = ";
SafeDouble (a);
cout << "b = ";
SafeDouble (b);
cout << "\nEnter operation sign: +, -, * or /\n";
char op;
cin >> op;
cin.sync();
switch (op)
{
case '+': cout << a << " + " << b << " = " << a + b;
break;
case '-': cout << a << " - " << b << " = " << a - b;
break;
case '*': cout << a << " - " << b << " = " << a * b;
break;
case '/': if (b == 0.0)
cout << "Division by zero";
else
cout << a << " / " << b << " = " << a / b;
break;
default: cout << "Incorrect operation sign";
}
cin.get();
return 0;
}
//-----------------------------------------------------------------------------