The following is my code:
#include <iostream>
using namespace std;
int main() {
int num;
cout<<"Enter a number: ";
cin>>num;
cout<<"The number is: "<<num;
return 0;
}
If I enter a character or a string instead of an integer on the prompt for cin>>num, the value of num is returned as 0 everytime. Is it because it has been implemented that way in C++ or am I missing some trivial concept? Any answer would be of great help.
This is a feature introduced in C++11. From cppreference;
before:
If extraction fails (e.g. if a letter was entered where a digit is expected), value is left unmodified and failbit is set. (until C++11)
now:
If extraction fails, zero is written to value and failbit is set. If extraction results in the value too large or too small to fit in value, std::numeric_limits::max() or std::numeric_limits::min() is written and failbit flag is set. (since c++11)
Note that before C++11 your code potentially invokes undefined behavior. If input fails you are using num uninitialized. In that case, 0 as output was just as valid as any other output (because undefined behavior is undefined).
std::basic_istream<CharT,Traits>::somehting then for now you can read that as std::istream::something, it looks a bit more complicated than it actually isIstreams objects have flags to detect bad input: whenever bad input is passed to cin there'll be a bad input flag set. By calling cin.fail() and checking if it evaluates to true you can actively monitor if input wasn't correct. In that case, cin will assign value 0 to the variable you passed.
