How to read end of line?
 

I'm wanting the program to read a line out of file. I wish c++ had .eoln()!

I get: test.cpp:10: no match for `std::ifstream& != char' operator
obviously because I'm comparing the wrong data types.

Is there a function in c++, like in pascal, so you can detect the end of a line? I know in pascal it would be like infile.eoln(), but that doesn't work in c++.

Any help will be appreciated,

Thanks
Andy

Re: How to read end of line?
 

If you're trying to read from a file, use some function that will read from a file. Sitting at the beginning of a file and waiting for the end to come will not do much.

#include <iostream>

#include <fstream>

#include <string>

using namespace std;



int main ()

{

   string line;

   ifstream infile("test_file.txt");

   while ( getline(infile, line) )

   {

      cout << line << endl;

   }

   return 0;

}

Re: How to read end of line?
 

^yeah but what if the line can't be treated as a string?

On the line, I am wanting to get, there is going to be 1 to 5 double's. Since I don't know how many doubles are going to be on that line, I just need to grab the whole line.

Then I was going to fill an array with how ever many double's were on that line:

double arr[5];
int i;

for (i=0; not end of the line; ++i)
{infile>>arr[i];
}

Re: How to read end of line?
 

I'd go with a vector of a vector of doubles. The vector of doubles per line, and the vector of these vectors for each line.

Re: How to read end of line?
 

A sample.

#include <iostream>

#include <fstream>

#include <string>

#include <sstream>

#include <vector>

using namespace std;



int main()

{

   vector < vector < double > > info;

   ifstream file("file.txt");

   string line;

   while ( getline(file, line) )

   {

      vector < double > data;

      double value;

      istringstream iss(line);

      while (iss >> value)

      {

         data.push_back(value);

      }

      info.push_back(data);

   }

   for ( vector < vector < double > > :: size_type i = 0, size = info.size(); i < size; ++i)

   {

      cout << "line " << i + 1 << ": ";

      for ( vector < double > :: size_type j = 0, length = info[i].size(); j < length; ++j)

      {

         cout << info[i][j] << " ";

      }

      cout << endl;

   }

   return 0;

}



/* file.txt

1 2 3

4 5 6 7 8 9

10 11 12 13

14

15 16

*/



/* my output

line 1: 1 2 3

line 2: 4 5 6 7 8 9

line 3: 10 11 12 13

line 4: 14

line 5: 15 16

*/

There are probably better/easier ways to go about iterating through the loop, and I'm sure someone will let me know.

Re: How to read end of line?
 

Okay, sorry, I'm still learning about all this stuff and I thought if you knew how many items were going to be used, then use an array?

So you think I should do something like this...

double num;
vector<double> charges[0];

while (not end of the line)
{ file>>num;
charges.push_back(num);
}

Am I on the right track, or am I way off?

[EDIT] ...reading the code you posted...

Re: How to read end of line?
 

By the way, since we're posting at similar times, I thought I'd bring this up FWIW:

http://www.eskimo.com/~scs/C-faq/q12.2.html

Re: How to read end of line?
 

Thanks man! I wish I would have known that a couple programs ago, lol.

In my CS class, we haven't learned istringstream yet, so I don't know how I would have known how to do that.

So all istringstream does is make each number on that one line ready to be stored into a variable?

I appreciate your help.

Re: How to read end of line?
 

It is used to do things like >> from a string instead of cin or an ifstream.

So the code I posted reads the whole line into a string, rather than going one value at a time (because both a newline and a space are whitespace characters, it might be tougher to distinguish using other means). Then it parses each double via the stringstream and >> operator.