[RESOLVED] writing to file and newline( endl and '/n'

[TheLionKing]

am having problem asking for a new line when writing to a txt file...not working with std::endl and not with '\n'...i COMMENTED IN THE CODE BELOW WHERE THE PROBLEM ARISES....

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

int main (){
std::vector<std::vector<int> > test = {{1,2,3,0,3},
                                      { 0,1,3,0,0},
                                      {0,0,0,0,0},
                                      {1,2,3,0,3},
                                     {0,3,4,4,4},};
/*
for (int i = 0; i< 5; i++)
for (int k = 0; k <3; k++)
    std::cout<<test[i][k];
std::cout<<std::endl;
std::cout<<test[4][3]; */

std::vector<int> f = {1,2,3,4,5,6,7,8,9,10};
int n = 0;
for (int i = 0; i < f.size(); i++)
{
     if (n <= 2)
     {
         std::cout<<f[i]<<", "; n++; 
     }
     else { n= 1; std::cout<<std::endl<<std::endl<<f[i]<<", ";
                       }
}

std::fstream file;
	file.open("oppose.txt", std::ios::in | std::ios::out | std::ios::trunc);
	if (file.is_open()){

        int k = 0;
for (int i = 0; i < f.size(); i++)
{
     if (k < 70)
     {
         file<<f[i]<<"    "<<std::endl; k++;// ASKING FOR NEWLINE HERE GIVES GOOD RESULT
     }
     else { k=1;
 file<<'n'<<'\n'<<'\n'<<f[i]<<" ,"; //ALL THE NEWLINES AM ASKING HERE ARE IGNORED! WHY?
                       }
}
	std::cout<<"writing to file successful!";
	}


	else
        {std::cout<<"could not write to file...";}

return 0;
}

[Eri523]

Have you verified by debugging that the line in question gets executed at all? Regarding the code as you posted it, I'd take any bet that it does not...

[2kaud]

Please use code tags for c++ code and not HTML tags. Go advanced, select code and click '#'

Have you used the debugger to see if the else part of the if statement is actually being executed? Does k ever get greater than 70?

[TheLionKing]

I notice the k<70 error...am gonna try it again..thanks

[2kaud]

I'm not sure what you are trying to accomplish with

int k = 0;
     for (int i = 0; i < f.size(); i++) {
          if (k < 70) {
             file << f[i] << "    " << std::endl;
             k++;// ASKING FOR NEWLINE HERE GIVES GOOD RESULT
         } else { 
             k=1;
             file << 'n' << '\n' << '\n' << f[i] << " ,";
            //ALL THE NEWLINES AM ASKING HERE ARE IGNORED! WHY?
        }
    }

but it can be simplied to

for (int i = 0; i < f.size(); i++) {
     if ((i + 1) % 70) {
        file << f[i] << std::endl;
     } else {
        file << "\n\n" << f[i] << " ,";
     }
}

[TheLionKing]

HI 2kaud...good evening master...please...i don't get what you mean by if(i+1)%70....in words...if i plus one divided by 70 gives no remainder??? is that what you mean?

[2kaud]

% is the mod operator. It returns the remainder for integer numbers. So 3 % 70 returns 3. 71 % 70 returns 1, 0 % 70 returns 0 and 70 % 70 returns 0. So i starts at 0. So when i is 0 to 68, i + 1 is 1 to 69 and 1 to 69 mod 70 gives a non-zero result so the if condition will be true. When i is 69, i + 1 is 70 and 70 % 70 gives 0 so the if condition is false and the else statement is executed. When i is 70, i + 1 is 71 and 71 % 70 is 1 which is positive so the cycle repeats until i is 139 (139 +1 is 140 and 140 % 70 is 0).

http://msdn.microsoft.com/en-us/libr...=vs.71%29.aspx