PLEASE HELP!

[coinjo]

#include<fstream>
using namespace std;

int main()
{
ifstream indata;
ofstream outdata;

indata.open("D:\\C++\\New Folder\\infile.txt");
outdata.open("D:\\C++\\New Folder\\outfile.txt");

int a=0;
int i=0;
int b=0;

while(a<9)
{
indata>>i;
b=i;
outdata<<b<<" ";
a=a+1;
}
indata.close();
outdata.close();

return 0;

}

This is in the infile.txt

1
2
3
4
5
6
7
8
9

The infile.txt and the outfile.txt are both in the same folder but when
i run the program even after deleting the outfile.txt it shows this:
0 0 0 0 0 0 0 0 0

rather than this:
1 2 3 4 5 6 7 8 9

PLEASE HELP!

[mlimber]

coinjo wrote:

#include<fstream>
using namespace std;

int main()
{
ifstream indata;
ofstream outdata;

indata.open("D:\\C++\\New Folder\\infile.txt");
outdata.open("D:\\C++\\New Folder\\outfile.txt");
Prefer to open with the constructors:

ifstream indata( "in.txt" );
ofstream outdata( "out.txt" );

Note that you didn't check if the open succeeded, and I'm guessing
that's your problem (perhaps because of the space in the pathname).

int a=0;
int i=0;
int b=0;
Don't declare variables until you use them. i and b should be declared
inside the loop. (Actually, you don't need both of them in the first
place.)

while(a<9)
{
indata>>i;
b=i;
outdata<<b<<" ";
a=a+1;
"++a;" is more conventional. Even better would be a for loop rather
than a while loop.
}
You need to check for read failures (due to disk errors, end of file,
etc.). Prefer the canonical form:

while( indata >> i )
{
outdata << i << ' ';
}

You could put a check for the iteration cound in the while condition if
the input file could have more than 9 pieces of data and you only want
the first 9 of them:

while( (indata >> i) && (a++ < 9) )
{
outdata << i << ' ';
}
indata.close();
outdata.close();

[snip]

Unnecessary. The destructors do this automatically. You should
generally only use close when you need to close the file before the end
of scope.
Cheers! --M

[Pep]

mlimber wrote:

coinjo wrote:

#include<fstream>
using namespace std;

int main()
{
ifstream indata;
ofstream outdata;

indata.open("D:\\C++\\New Folder\\infile.txt");
outdata.open("D:\\C++\\New Folder\\outfile.txt");

Prefer to open with the constructors:

ifstream indata( "in.txt" );
ofstream outdata( "out.txt" );

Note that you didn't check if the open succeeded, and I'm guessing
that's your problem (perhaps because of the space in the pathname).

int a=0;
int i=0;
int b=0;

Don't declare variables until you use them. i and b should be declared
inside the loop. (Actually, you don't need both of them in the first
place.)

while(a<9)
{
indata>>i;
b=i;
outdata<<b<<" ";
a=a+1;

"++a;" is more conventional. Even better would be a for loop rather
than a while loop.

}

You need to check for read failures (due to disk errors, end of file,
etc.). Prefer the canonical form:

while( indata >> i )
{
outdata << i << ' ';
}

You could put a check for the iteration cound in the while condition if
the input file could have more than 9 pieces of data and you only want
the first 9 of them:

while( (indata >> i) && (a++ < 9) )
{
outdata << i << ' ';
}

indata.close();
outdata.close();

[snip]

Unnecessary. The destructors do this automatically. You should
generally only use close when you need to close the file before the end
of scope.
Cheers! --M

I would agree with this. Initially I thought this might be a problem local
to windows as I ran the program on linux and had no problems with it. Then
I ran on windows with no problems until I deleted the input file.

Ho hum.