How can you check if a value entered is numeric?

Question

#include<iostream>
using namespace std;
int main()
{
    double money;
    cout << "Input the sum of money: ";
    cin >> money;
....

I have been trying to check if the value entered is a numeric value so that i can display an error message if another value (alphabetic letter) is entered and the code will loop back to ask for the input again (the money)

What's with the all caps title? – Mysticial Jan 08 '14 at 21:42 — Mysticial, Jan 08 '14 at 21:42
@Mysticial, What all caps title? – chris Jan 08 '14 at 21:42 — chris, Jan 08 '14 at 21:42

score 2 · Answer 1 · answered Jan 08 '14 at 21:43

2

while ( ( cin >> money ) == false )
{
...
}

answered Jan 08 '14 at 21:43

kuhar

338
1
2
10

Vlad from Moscow · Answer 2 · 2014-01-08T21:56:27.527

2

You can check the state of the stream after the input. For example

if ( !( std::cin >> money ) ) std::cout << "Oh, I made a mistake!\n";

And if you want to repeat the input you should call

std::cin.clear();
std::cin.ignore( std::numeric_limits<std::streamsize>::max(), '\n' );

Do not forget to include header <limits>

edited Jan 08 '14 at 21:56

answered Jan 08 '14 at 21:43

Vlad from Moscow

301,070
26
186
335

How can you check if a value entered is numeric?

2 Answers2