Capture and convert stings from file and perform numerical operations

Question

This is my code:

int main()
{
std::ifstream myfile;
myfile.open("ex.txt");
std::string a;
while(myfile.eof()!=1)
{
    getline(myfile,a,',');
    int i = stoi(a);
    if (!(i%2))
      std::cout<<a<<std::endl;
}

}

Basically I have a text file with comma separated integers. I now wish to display even of these integers. I am running the code on Xcode , Apple LLVM. I get the correct output but Xcode shows some wierd exception:

libc++abi.dylib: terminating with uncaught exception of type std::invalid_argument: stoi: no conversion Program ended with exit code: 0

This message comes with a breakpoint on the stoi command. Whats happening? And how can I do this smoothly?

Edit: Input text File.

5,8,4,8,0,8,4,3,0,7,8,3,6,2,9,7,3,0,9,0,1,9,2,4,5,4,9,8,4,3,0,9,3,3,5,1,1,8,6,3,4,6,8,2,0,2,6,2,1,6,6,1,9,4,1,1,2,9,3,0,3,2,3,9,4,8,0,3,2,2,6,9,1,1,8,1,0,3,6,3,0,3,2,8,6,5,0,3,7,4,3,3,6,0,1,2,2,8,2,5,1,0,0,2,8,8,3,3,8,9,2,3,6,2,5,0,2,4,6,2,6,1,0,2,6,7,1,2,1,8,5,2,2,3,4,2,7,1,7,3,3,8,9,3,2,9,9,5,1,3,4,2,2,0,1,3,0,8,3,4,7,4,5,5,6,4,0,7,8,0,1,1,8,5,2,7,4,4,6,3,4,4,8,3,4,1,1,1,9,2,5,1,3,4,2,6,4,8,7,2,

No \n i.e. linee changes

0x499602D2 0x499602D2 · Accepted Answer · 2014-01-09T13:55:42

I believe this has to do with the fact that you're using while (!eof()). This is an erroneous expression to use as a condition as it doesn't conform to the intended functionality of IOStreams. You should be checking if the input succeeded before the input is performed:

while (std::getline(myfile, a, ','))

Doing otherwise causes the stream to reach the end-of-file and for the string a to be without a value. This empty string is then passed to std::stoi, causing an exception to be thrown.

Capture and convert stings from file and perform numerical operations

2 Answers