How to test whether stringstream operator>> has parsed a bad type and skip it

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The following code works well to skip the bad word and collect the valid double values

istringstream iss("2.832 1.3067 nana 1.678");
double num = 0;
while(iss >> num || !iss.eof()) {
    if(iss.fail()) {
        iss.clear();
        string dummy;
        iss >> dummy;
        continue;
    }
    cout << num << endl;
}

Here’s a fully working sample.

Your sample almost got it right, it was just missing to consume the invalid input field from the stream after detecting it’s wrong format 

 if (parser.fail()) {
     std::cout << "Failed!" << std::endl;
     parser.clear();
     string dummy;
     parser >> dummy;
 }

In your case the extraction will try to read again from "nana" for the last iteration, hence the last two lines in the output.

Also note the trickery about iostream::fail() and how to actually test for iostream::eof() in my 1st sample. There’s a well known Q&A, why simple testing for EOF as a loop condition is considered wrong. And it answers well, how to break the input loop when unexpected/invalid values were encountered. But just how to skip/ignore invalid input fields isn’t explained there (and wasn’t asked for).

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