Why does this while loop never evaluate to true?

Question

If the file has a list of coordinates and a character:

(1,2,3,A)
// blah blah
(10,20,30,B)
(11,22,33,C)

the expression in the while loop never evaluates to true, Why is this?

string str = "";
char aa, cc, ee, gg, hh, ii;
int bb, dd, ff;
while(cin >> aa >> bb >> cc >> dd >> ee >> ff >> gg >> hh >> ii ||
      cin >> str) {
    if(str != "") {
        cout << str << endl;
    }
    else {
        cout << aa << " " << bb << " " << cc << " " << dd << " " << ee << " " <<  ff << " " << gg << " " << hh << " " << ii << endl;
    }
}

try to avoid telling us that things "do not work", instead, describe the specific errors/incorrect output that you get. It makes it easier for us to diagnose the problem — Sam I am says Reinstate Monica, Sep 26 '13 at 19:05
Sorry! I just edited it. For some reason, my while loop never evaluates to true. — thedanyaal, Sep 26 '13 at 19:07

score 3 · Answer 1 · answered Sep 26 '13 at 19:07

Once you stream has gone into fail-state, i.e., std::ios_base::failbit is set, the stream won't do anything until the stream got cleared. That is, if your first input failed, the second input will fail, too. What would work is spinning things around: first read the string and then using a string stream to see if it decodes into the constituents.

Why does this while loop never evaluate to true?

1 Answers1