How to check if the input is a valid integer without any other chars?

Question

#include 
#include 

using namespace std;

int main()
{
    int x;
    cout << \"5 + 4 = \";
    while(!(cin >> x)){
               


        

Answer 1

You have a line oriented input, so you should probably be using getline. Something like:

bool
getIntFromLine( std::istream& source, int& results )
{
    std::string line;
    std::getline( source, line );
    std::istringstream parse( source ? line : "" );
    return parse >> results >> std::ws && parse.get() == EOF;
}

should do the trick.

Using this, your loop would be:

while ( !getIntFromLine( std::istream, x ) ) {
    std::cout << "Error, please try again." << std::endl;
}

Note that this technique also means that you don't have to worry about clearing the error or resynchronizing the input.