Stringstream to vector<int>

Question

I'm wondering what the best way to write from an std::stringstream into a vector<int>.

Here's an example of what's in the stringstream: "31 #00 532 53 803 33 534 23 37"

Here's what I've got:

int buffer = 0;
vector<int> analogueReadings;
stringstream output;

 while(output >> buffer)
     analogueReadings.push_back(buffer);

However what seems to happen is, it reads the first thing, then it gets to #00 and returns 0 because it's not a number.

Ideally, what I want is, it gets to a # and then just skips all characters until the next whitespace. Is this possible with flags or something?

Thanks.

Answer 1

#include <iostream>
#include <sstream>
#include <vector>

int main ( int, char ** )
{
    std::istringstream reader("31 #00 532 53 803 33 534 23 37");
    std::vector<int> numbers;
    do
    {
        // read as many numbers as possible.
        for (int number; reader >> number;) {
            numbers.push_back(number);
        }
        // consume and discard token from stream.
        if (reader.fail())
        {
            reader.clear();
            std::string token;
            reader >> token;
        }
    }
    while (!reader.eof());

    for (std::size_t i=0; i < numbers.size(); ++i) {
        std::cout << numbers[i] << std::endl;
    }
}

Answer 2

You need to test if you got a number or not. use the answer from here:

How to determine if a string is a number with C++?

#include <iostream>
#include <sstream>
#include <vector>
using namespace std;

bool is_number(const std::string& s){
   std::string::const_iterator it = s.begin();
   while (it != s.end() && std::isdigit(*it)) ++it;
   return !s.empty() && it == s.end();
}
int main ()
{
    vector<int> analogueReadings;
    std::istringstream output("31 #00 532 04hello 099 53 803 33 534 23 37");

    std::string tmpbuff;
    while(output >> tmpbuff){
      if (is_number(tmpbuff)){
         int num;
         stringstream(tmpbuff)>>num;
         analogueReadings.push_back(num);
       }
    }
}

the result is 31 532 99 53 803 33 534 23 37

Also, important drawbacks of using lexical casts like this is described here: How to parse a string to an int in C++? , where an alternative to tringstream(tmpbuff)>>num is given.

For example 04hello becomes 4 and 7.4e55 becomes 7. There are also terrible problems with underflow and underflow. The clean solution by André Caron converts

25 10000000000 77 0 0

into

25 0 0 

on my system. Note that also 77 is missing!

Answer 3

No loops version:

#include <iostream>
#include <vector>
#include <iterator>
#include <algorithm>
#include <sstream>

using namespace std;

class IntegerFiller
{
    vector<int> &m_vec;
public:
    IntegerFiller(vector<int> &vec): m_vec(vec) {}

    void operator()(const std::string &str)
    {
        stringstream ss(str);
        int n;
        ss >> n;
        if ( !ss.fail() )
            m_vec.push_back(n);
    }
};

int main()
{
    vector<int> numbers;
    IntegerFiller filler(numbers);
    for_each(istream_iterator<string>(cin), istream_iterator<string>(), filler);
    copy(numbers.begin(), numbers.end(), ostream_iterator<int>(cout, " "));
    return 0;
}

Answer 4

I think the best method would be to

#include <string>
#include <sstream>
#include <vector>

using namespace std;   

int main()
{   
  string numbers = "23,24,27,28";   
  vector<int> integers;   
  stringstream s(numbers);   
  char ch;   
  int a;   
  while(s>>a>>ch) integers.push_back(a);   //s >> reads int char pair 
  s>>a;                                    // reads the last int
  integers.push_back(a); 

  for(int i = 0; i < integers.size(); i++) cout << integers[i] << "\n";
}