Reading integers from an unorganized text file

Question

#include <iostream>
#include <fstream>
#include <string>
#include <cctype> // isdigit();
using namespace std;
int main()
{
    ifstream fin;
    fin.open("Sayı.txt");
    while (!fin.eof()){
        string word;
        int n;
        fin >> word;  //First i read it as a string.
        if (isdigit(word[0])){ //checks whether is it an int or not
            fin.unget(); //
            fin >> n;  // if its a int read it as an int
            cout << n << endl;
        }
    }
}

Suppose the text file is something like this:

100200300 Glass
Oven 400500601

My aim is simply to read integers from that text file and show them in console. So the output should be like

100200300
400500601

You can see my attempt above.As output i get only the last digit of integers.Here's a sample output:

0
1

What do you think `unget()` is doing? Perhaps look at the documentation. — zindorsky, Jun 09 '13 at 17:30
[`while (!eof())` is wrong.](http://stackoverflow.com/questions/5605125/why-is-iostreameof-inside-a-loop-condition-considered-wrong) — chris, Jun 09 '13 at 17:30
unget() drops the temporarily stored variable on fin.Or thats what i think it does. — SpiderRico, Jun 09 '13 at 17:33

score 1 · Accepted Answer · answered Jun 09 '13 at 18:08

Simple just try converting the string read to an int using string streams, if it fails then it isn't an integer , otherwise it is an integer.

 ifstream fin;
    istringstream iss;
    fin.open("Say1.txt");

    string word;
    while (fin>>word )
    {

        int n=NULL;        
        iss.str(word);

        iss>>n;

        if (!iss.fail())
        cout<<n<<endl;

        iss.clear();


    }

score 0 · Answer 2 · answered Jun 09 '13 at 17:33

I think the following should do what you want (untested code):

int c;
while ((fin >> std::ws, c = fin.peek()) != EOF)
{
  if (is_digit(c))
  {
    int n;
    fin >> n;
    std::cout << n << std::endl;
  }
  else
  {
    std::string s;
    fin >> s;
  }
}

Reading integers from an unorganized text file

2 Answers2