Thread: question: i/o data form .txt or .xls files ??

What did I tell you about code tags?

Code:

while (!data.eof())

Bad idea. http://faq.cprogramming.com/cgi-bin/...&id=1043284351

in this code i import and export "line" from the files which is not what i'm looking for, i want to import and export individual integers from the files

Well, here's what your code does right now.

• Read lines until the end of the input file.
• Write the last line read to the output file.

In effect, it writes the last line of the input file to the output file.

What you need to do is to read integers, not lines. Since you know the format of the input file, you could probably

• read the integer a from the input file;
• read the integer b from the input file;
• calculate the sum of these two numbers, storing the result in c;
• write a, b, and c to the output file.

Does that give you any ideas?

Code:

// Assuming only 26 numbers on 1 line
#include <fstream>
#include <iostream>
#include <string>
#include <sstream>

using namespace std;

int main(void)
{
	ifstream input("in.txt");
	ofstream output("out.txt");

	string     line;
	stringstream ss;
	double num;
	double sum;
	char   idx;

	while ( getline(input, line) )
	{
		ss << line;
		sum = 0;
		idx = 'a';

		while (ss >> num)
		{
			output << idx++ << '=' << num << ends;
			sum += num;
		}

		output << idx << '=' << sum << endl;
		ss.clear();
	}

	input.close();
	output.close();

	return 0;
}

in.txt

Code:

3 5 7 6 9
4 5 6 3 2 1 3 43 66 34 12 76 34
1 2 3

out.txt

Code:

a=3 b=5 c=7 d=6 e=9 f=30
a=4 b=5 c=6 d=3 e=2 f=1 g=3 h=43 i=66 j=34 k=12 l=76 m=34 n=289
a=1 b=2 c=3 d=6

Yes, well, that's one way to do it. However, your variable names are pretty terse -- it's generally best to use longer names when you're posting code for others to learn from. And really, that's not the easiest code for someone to learn from; it's too complicated. You have to figure that someone who can't read two numbers, add them, and print them isn't going to learn much from something like that.

In addition, if you're going to all of the trouble to use a vector, don't hard-code the size of the vector into the program. That's one nice thing about vectors -- they can expand to hold new data as you see fit.

[edit] On the other hand, you don't need to remember previous numbers at all. See below. [/edit]

Really, it's quite simple. As long as you know there are two numbers:

Code:

int a, b, c;
input >> a >> b;
c = a + b;
output << a << ' ' << b << ' ' << c << '\n';

If you want to sum some arbitrary number of numbers, it's easier to keep a running total. With only one line, something like this would work.

Code:

int var, sum = 0;
while(input >> var) {
    output << var << ' ';
    sum += var;
}

output << sum << '\n';

With multiple lines, it might be necessary to read each line separately and parse that string with stringstreams as knave has shown.

you're right dwks i didn't understand a lot from the code and there are a lot of new codes that I've to understand before i used it...

Sorry if I sounded insulting, but knave's code really was pretty complicated before [s]he edited it.

@knave: One last thing: you do know that the std::ends manipulator function prints a NULL, right?

Code:

output << idx++ << '=' << num << ends;

I would think a simple space would be better . . .

Oh, and how did you syntax highlight that code?