Thread: parsing problem

I'm writing a console app to ask the users for the edges of a graph and compute the MST for the give nodes but am having trouble parsing the input. The data is give in the form:

(node1,node2) weight

and the following code will extract the 2 nodes but I constantly get an out_of_range exception when trying to get the get the weight.

Code:

int main()  {
  string cmd;
  int startIdx, endIdx, length;
  int vert1, vert2, weight;

  // command loop, ends with EOF
  cout << ": ";
  while(true) {
    cin >> cmd;
    
    // terminate on EOF
    if(cin.eof() != 0) {
      cout << endl;
      return 0;
    }

    // parse input    
    length = cmd.capacity() - 1;
    startIdx = cmd.find('(', 0);
    endIdx = cmd.find(',', startIdx);
    vert1 = atoi((cmd.substr(startIdx + 1, endIdx - startIdx - 1)).c_str());
  
    startIdx = endIdx;
    endIdx = cmd.find(')', startIdx);
    vert2 = atoi((cmd.substr(startIdx + 1, endIdx - startIdx - 1)).c_str());

    startIdx = endIdx + 1;
    endIdx = length;
    weight = atoi((cmd.substr(startIdx + 1, endIdx - startIdx)).c_str());

    cin.clear();
    cin.ignore(numeric_limits<streamsize>::max(), '\n');

cout << "From: " << vert1 << "  To: " << vert2 << "  Weight: " << weight << endl;
  
  
    cout << ": ";
  }

  return 0;
}

Everything I've read says I can call substr() with the start index alone and it will return a string from the index to the end of the string but that gives me the same exception. I've tried with a length of 1 when I provide a 4-digit weight (so I know I'm not running past the end of the string) and still get the same exception.

Could someone please explain what I'm not getting about substr()?

Thanks.

Jasen

>> cin >> cmd;
That will not read past white spaces. You can replace it with the following to read an entire line at a time:
>> getline(cin, cmd);

You should also check the return value of find() for string::npos in order to detect bad input.

gg

Ah, great. Knew it had to be something silly on my part.

Thanks!