Hi!
Please, I really need help with a problem.
I need to read numbers (float type) from a file. Numbers are arranged in rows, I don't know how many in each row, there may be a large number of numbers (milions). How can I read each row of numbers, for example to know how many are in each line?
That's because in C++ there is no eoln function, to detect end of line.
My text file can be:

2.345 1 100.5
23.45 12
11.2 100.2345789 1000 1 1 1
2 3 4 5
1
2
7

If I read every row in a string, I can extract from there every number, but if in a row there are many, many numbers, I have a memory restriction problem, so I can't declare a string char s[100 000 000], maybe bigger, for example.

I wrote this code, but I have some problems (except the problem detailed in rows before):

# include <fstream.h>
using namespace std;
long x,i;
long double a;
char s[1000000], *p, b[1000000], d[]=" ";
ifstream f("date.in");
ofstream g("date.out");
int main()
{ do
    { f.get(s,1000000);
      f.get();
      p=strchr(s,' ');
      while (p)
      { i=p-s;
        strncpy(b,s,1000000);
        b[i]='\n';
        a=atof(b);
        g<<a<<' ';
        strcpy(s,s+i+1);
        p=strchr(s,' ');
      }
      g<<atof(s)<<' '<<endl;
    } while (!f.eof());
}

1- atof(b) return 100.235 if my string b is "100.2345789"
2- My code reads an extra row, it reads a null string, in the end of my input file, so it converts it in 0 and writes this 0 in the end of my date.out, like this:

2.345 1 100.5 
23.45 12 
11.2 100.235 1000 1 1 1 
2 3 4 5 
1 
2 
7 
0 

If somebody is patient enough to read my text , PLEASE help me!
Thanks a lot!!!

Edited 3 Years Ago by mike_2000_17: Fixed formatting

Presumably each line is processed individually, in which case you can simply read a line at a time and then parse it. As an example, this program would echo the file to stdout:

#include <fstream>
#include <iostream>
#include <sstream>
#include <string>

int main()
{
  std::ifstream in("file");

  if (in) {
    std::string line;

    while (std::getline(in, line)) {
      // Parse the line using a string stream
      std::istringstream row(line);
      double field;

      while (row>> field)
        std::cout<< field <<'\t';

      std::cout<<'\n';
    }
  }
}

You can try out this. Only you cannot press enter after the ending line.

#include<iostream>
#include<fstream>
using namespce std;

int main() {
      int x=0, y=1;
      char ch;
      ifstream in("file.txt");
      while(in.get(ch))
           {
              if (ch!='\n' && isspace(ch))
                   {
                      x++;
                   }
              else if (ch=='\n')
                  {
                     cout<<"Line"<<y<<":"<<x+1<<endl;
                     x=0;
                     y++;
                   }
              }
            return 0;
}

Edited 3 Years Ago by Reverend Jim: Fixed formatting

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