Here is my piece of code which is bothering me really hard.
Basically what this does is read string from of data file.This piece which some how does not read the end of file after all the date in the file are being read. it goes round again and fill the matrix (actually vector) with the last 'num' variable it had read in the loop it had gone through last time. cTable and dTable are filled with same num variable it had read in the previous loop cycle.
for example, if 5 is the last integer 'num' read than it comes round and fill the vectores with 5s.
Case 'E' is the last case in this switch statement and of course 'ch' still has 'E' in it.


do
   {
   input >> ch;        
   switch (ch)
      {
 
   case 'E':  // To read the cofficient of linear equations and find the solutions.
      
       input >> bROW;
       
       if ( bROW > MAX && bROW <= 0)
          YesNo(); // if out of bound, asks if want to do it again with another test file.
          ClearSMat(bROW);  // clears the vectors for next use
           for(int i = 0; i < bROW; i++)
           {
               for(int j = 0; j <= bROW; j++)
               {
                   input >> num;
                   if (j == bROW)
                       dTable[i] = num;
                   else
                   cTable[i][j] = num;              
               }
           }           
            SystemOfEqMatrix(bROW);// print the system of linear equations in matrix form
            FindSolution(bROW);       // find the solution of the linear equations
            SolutionMatrix(bROW);    // print the solutions    
            //cin.ignore(1, '/n');
        break;        
    }//end of switch
   } while (!input.eof());//end of do - while  

does not read the end of file and goes infinitely.

do
   {
   input >> ch;        
     cout<<"ch is "<<ch;
    input>>bRow;
   cout<<"bRow is "<<bRow;
   input>>num;
  cout<<"num is "<<num;
   } while (!input.eof());//end of do - while 


Can you see what's the output of this?

TechGuy, It does what it is suppose to do... it gives me correct solution and correct matrix.. but somehow it does not read eof() and goes back to fill the vectors again with the last digit which it had already done with. I tested with couple of files to see if it is got to do with the files, again it does the same thing. It simply does not read the eof() of the files I am testing with.
this is the test file I am using. I for the inverse and E for system of equation. After I and E is the rows of the matrix.And I have put cursor at the ennd of the file too.

I 3
1 1 0
4 3 0
2 1 -1

I 2
2 -4
4 -7

I 3
1 1 0
1 2 1
2 3 2

E 3
1 2 1 8
2 1 -1 1
1 1 -2 -3

E 3
1 1 0 20
1 2 1 30
2 3 2 55
thanks!!

Does your code read all the matrices or it just reads the first one?

maverick, there are two cases I and E.. I gave here just E case cause  E is the last case and after it read data from the file for case ' E' it should reach to the end of file. Ok here is my whole code in main()

void main()
{
    int aROW, bROW, num ;
    char ch;
    string fileName;
    ifstream input;

   cout << "Enter the file name : ";
   cin >> fileName;

   // Attempt to open a disk file  
   input.open(fileName.data());
   if (!input.is_open())
   {
      cout << "\nFile could not be opened!\n" << endl;
      exit(1); // abort execution
   }
 
   do
   {
   input >> ch;       
   switch (ch)
      {
   case 'I': // find the inverse of the given matrix, if it is ivertible
          input >> aROW;
          if ( aROW > MAX && aROW <= 0)
           YesNo();
           ClearIMat(aROW);               
           for(int i = 0; i < aROW; i++)
           {
             
               for(int j = 0; j < aROW; j++)
               {
                   input >> num;
                   aTable[i][j] = num;             
               }
           }
           OriginalToInverse(aROW);
           //identity matrix
           for(int i = 0; i < aROW; i++)
           {
               for(int j = 0; j < aROW; j++)
               {
                   if ( i == j)
                       bTable[i][j] = 1;
                   else
                       bTable[i][j] = 0;
               }
           } 
              FindInverse(aROW);   
              InverseMatrix(aROW);
              break;

   case 'E':  // find the solution of the linear equations
     
       input >> bROW;
      
       if ( bROW > MAX && bROW <= 0)
          YesNo();
          ClearSMat(bROW);
           for(int i = 0; i < bROW; i++)
           {
               for(int j = 0; j <= bROW; j++)
               {
                   input >> num;
                   //if (num == 0)
                     //  break;
                   if (j == bROW)
                       dTable[i] = num;
                   else
                   cTable[i][j] = num;             
               }
           }          
            SystemOfEqMatrix(bROW);// print the system of linear equations in matrix form
            FindSolution(bROW);       // find the solution of the linear equations
            SolutionMatrix(bROW);    // print the solutions   
            //cin.ignore(1, '/n');
            break;       
    }//end of switch
   } while (!input.eof());//end of do - while
  input.close();
} // end of main

Does your code read all the matrices or just the first one?

BTW, cTable is for storing the coefficient and dTable for storing constants after = in the equations.

try using
  while(input>>ch)
  {




}
see if that works, i dont have c++ compiler with me right now...so can't verify it.

Hi,
I had the exact same question four years back.

eof returns true only after a read effort is made after end of file.
This code:
do { read; do other stuff} while ( !eof)
with this file:
1
2

Your code reads value 2, finishes do, checks to see if eof is true....which it is not right now, because you successfully read 2. The code goes back to do...tries to read something....doesn't have anything....the variable still holds the value of 2....it is ONLY THIS TIME eof is true....the while loop terminates.

There are two ways of getting around this:
1> as techguy suggested in the post above this: using while(inputstream>>stuff)
2> avoid do-while, use just while, and do
read; while(!inputstream.eof()){blah; read}

Gluck!

Thanks guys. I appreciate all of yours effort. finally I have found the mistake and corrected it. It was because of the test file I was using.  Apparently I  had  one too may 'enters' after the last digit in the test file which caused the char Var 'ch' to look for eof without any avail because I pushed down eof with my enters. Each time 'ch' could not find eof  it filled my matrices with the last digit it had read in the last loop.
and BTW both do-while and while loops work perfectly with the new test file.