How to say != 0-9 in c ++ [duplicate]

Answer 1

If the string was "0983" I want it to be true but if it was "124Test" I want it to remain false.

Saying that, an approach would be checking if a character is not a number, then return false, instead of checking every character until the end of the string.

bool b = true;
for(int i = 0; i < string.size(); i++)
{
    if(string.at(i) < '0' || string.at(i) > '9')
    {
        b = false;
        break;
    }
}