I am trying to use the atoi function in order to obtain conversion from string to int. The thing is that I have a string array which contains both integers and string values.
From what I've read, in order to get the error code from it, the function must return 0 :
string s = "ssss";
int i = atoi(s.c_str())
if (i == 0)
cout<<"error"<<endl;
end;
How should I proceed if my string value is 0 ?
Another issue is with this string : string s = "001_01_01_041_00.png". The atoi function returns the value 1. Shouldn't it return 0. Why does it return 1?
Answer
That is why atoi is unsafe to use. It doesn't detect and inform the program if the input is invalid.
C++11 has introduced std:stoi which is safe, as it throws exception if input is invalid in some way. There are also two other variants : std::stol and std:stoll. See the online documentation for detail:
Your code would become this:
try {
string s = "ssss";
int i = std::stoi(s); //don't call c_str()
//if (i == 0) no need to check!
std::cout << i << endl;
}
catch(std::exception const & e)
{
cout<<"error : " << e.what() <<endl;
}
Note that the runtime type of e could be either std::invalid_argument or std::out_of_range depending on the cause of the throw. You could just write two catch blocks if you want them to handle differently.