CODEWITHSUNDEEP
c++stringstream
user2138149
user2138149

Reputation: 16705

Stringstream read values into double fails?

New Problem

boost::tokenizer<> token(line); tokenizes decimal points! How can I stop this happening?

Previous problem below is now resolved.

I am trying to grab values from a stringstream into a vector of doubles.

std::ifstream filestream;
filestream.open("data.data");
if(filestream.is_open()){
    filestream.seekg(0, std::ios::beg);

    std::string line;
    std::vector<double> particle_state;
    particle_state.resize(6);
    while(filestream >> line){

        boost::tokenizer<> token(line);

        int i = -1;
        for(boost::tokenizer<>::iterator it=token.begin(); it!=token.end(); ++it){
            std::cout << *it << std::endl; // This prints the correct values from the file.

            if(i == -1){
                // Ommitted code
            }

            else{
                std::stringstream ss(*it);
                ss >> particle_state.at(i); // Offending code here?
            }
            i ++;
        }
        turbovector3 iPos(particle_state.at(0), particle_state.at(1), particle_state.at(2));
        turbovector3 iVel(particle_state.at(3), particle_state.at(4), particle_state.at(5));
        // AT THIS POINT: cout produces "(0,0,0)"
        std::cout << "ADDING: P=" << iPos << " V=" << iVel << std::endl;

    }


    filestream.close();
}

Contents of input file:

electron(0,0,0,0,0,0);
proton(1,0,0,0,0,0);
proton(0,1,0,0,0,0);

More on turbovector3:

turbovector3 is a mathematical vector class. (The important thing is that it works - essentially it is a vector with 3 items. It is initialised using the constructor with three doubles.)

Thanks in advance for help!

EDIT Modification of code:

std::stringstream ss(*it);
if(ss.fail()){
  std::cout << "FAIL!!!" << std::endl; // never happens
}
else{
  std::cout << ss.str() << std::endl; // correct value pops out
}
double me;
ss >> me;
std::cout << "double:" << me << std::endl; // correct value pops out again
particle_state.at(i) = me; // This doesn't work - why?

Upvotes: 0

Views: 1270

Answers (2)

user2138149
user2138149

Reputation: 16705

Solution! I fluked and found this site: Link

The solution is to change the tokenizer to this:

boost::char_delimiters_separator<char> sep(false,"(),;");
boost::tokenizer<> token(line,sep);

Now it works!

Upvotes: 0

Vlad Nestorov
Vlad Nestorov

Reputation: 360

Do you increment i in the omitted code? If not your else clause never gets called. Try outputting the stringstream buffer contents:

  std::cerr << ss.str();

Also check if reading from ss actually fails:

  if (ss.fail())
      std::cerr << "Error reading from string stream\n";

Upvotes: 1

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