istream and ostream detail.

[maadhuu]

Hello,
I would like to know as to how you can print a file in the reverse order
,starting from the last character to the 1st .Can I use istream or ostream
classes for this ??Or is there any better way of doing this in C++ ?
Thanking you,
Maadhuu.

 

[John Harrison]

Hello,
I would like to know as to how you can print a file in the reverse order
,starting from the last character to the 1st .Can I use istream or ostream
classes for this ??Or is there any better way of doing this in C++ ?
Thanking you,
Maadhuu.

Read the file into memory (say into a std:vector<char>) and then write
it out reversed. You can use istream and ostream for this if you also
use a little imagination.

john

 

[meagar]

I had a question like this once in college, with the arbitrary
requirement that we had to use a recursive function. What surprised me
was how much trouble it gave many people (we were second year at that
point)

#include <iostream>

void print_backwards(std::ifstream& fin, std:fstream& fout) {
char ch;
if (fin.get(ch)) {
print_backwards(fin, fout);
fout << ch;
}
}

int main() {
std::ifstream input('in.txt');
std:fstream output('out.txt');
print_backwards(input, output);
}

 

[Sandeep]

Maadhuu
meager wrote
Have you thought that this might have been a homework assignment as
well !!

 

[John Harrison]

I had a question like this once in college, with the arbitrary
requirement that we had to use a recursive function. What surprised me
was how much trouble it gave many people (we were second year at that
point)

#include <iostream>

void print_backwards(std::ifstream& fin, std:fstream& fout) {
char ch;
if (fin.get(ch)) {
print_backwards(fin, fout);
fout << ch;
}
}

int main() {
std::ifstream input('in.txt');
std:fstream output('out.txt');
print_backwards(input, output);
}

Ouch! Looks like real world considerations didn't count for much on your
course.

Of course the technique above is good for reversing any kind of sequence.

john

 

[meagar]

Yes, I did. If he uses my example, and the teacher hasn't explicitly
requested a recursive function, he should probably fail it :|

 

[maadhuu]

Hello people,
this is not a homework assignment by any means. I had just read about
reversing a file using istream and ostream operators in a book in the
library . I was curious to know how it would work .
Hence i asked this question .
Thanking you
Maadhuu