reading / writing files

I've just started playing with file io.

My raw data file contains the following:

-52.387596 61.659180 -2.277227
-52.341648 61.521450 -2.243313
.....

and I want to output a file such

#PSI Format 1.0
#
# column [0] = "x"
# column [1] = "y"
# column [2] = "z"
# column [3] = "Energy"
# column [4] = "Id"
# type[3] = byte

-52.3876 61.6592 -2.27723 0 0

As you can see from numbers in my outputed file the numbers have been rounded.

Q - How do I get around this?

Heres my code

Code:

#include <iostream>
#include <fstream>

#include <stdio.h>

using namespace std;


int main (int argv, char* arvc[]){
	
	char *sourceFileName = "start.xyz";
	char *destinationFileName = "finish.psi";

	fstream finput;
	fstream foutput;
	

	finput.open(sourceFileName, ios::in);
	foutput.open(destinationFileName, ios::out);

	int index = 0;
	string line;
	double
		x, y, z;

	if (finput.is_open() && foutput.is_open()){
		
		foutput << "#PSI Format 1.0" << endl;
		foutput << "#" << endl;
		foutput << "# column [0] = \"x\"" << endl;
		foutput << "# column [1] = \"y\"" << endl;
		foutput << "# column [2] = \"z\"" << endl;
		foutput << "# column [3] = \"Energy\"" << endl;
		foutput << "# column [4] = \"Id\"" << endl;
		foutput << "# type[3] = byte" << endl;
		foutput << "" << endl;

		while (!finput.eof()){
			
			finput >> x >> y >> z;
			foutput << x  << " " << y << " " << z << " " << 0 << " " << index << endl ;
			index++;
			
		}
			

		foutput.close();
		finput.close();



	}else{
		
		cout << "Error in opening eithe input or output files";

		if (finput.is_open ()){
			finput.close();
		}

		if (foutput.is_open()){
			foutput.close();
		}

	}


	cout << "Conversion undertaken";
	
	cin.ignore();
	cin.ignore ();
	return 1;
}

Perhaps I'm missing something real silly. I tried to make x,y,z floats as well but this didnt work either :-(

Thanks for pointers.

i believe you need to include the <iomanip> header and use setprecision(n). the default precision is 6 digits.

As I'm a real novice could you show some code as to how I would use this please?

I tried to use

Code:

finput.open(sourceFileName, ios::in);
finput.precision(8);

but I still have my number rounded. In fact cangin the precision doesnt seem to do anything to my inputed numbers.
Ta

Code:

#include <iomanip>
setprecision(n);       // Where n is the number of digits it's rounded to

nope afriad that doesnt appear to do anything.

Any other pointers?

its been a bit but i think this should do it.

Code:

foutput.setf(ios::fixed);
foutput<<setprecision(n)<<double;

Code:

			foutput << setprecision(8) << x  << " " << y << " " << z << " " << 0 << " " << index << endl ;

Afraid that doesnt appear to do the job either.

Thanks for responses guys.

However the issue at the moment is getting the correct numbers read in.

As mentioned -52.387596 61.659180 -2.277227 is read in as

-52.3876 61.6592 -2.27723

mm not sure whats going on. Just tried swoopies code.

I use the following input

-52.387596 61.659180 -2.277227
-52.341648 61.521450 -2.243313
-52.383675 61.594273 -2.273051
-52.337238 61.465927 -2.241447
-52.379589 61.535492 -2.273933
-52.371269 61.574524 -2.207932
-52.373951 61.478222 -2.279162

in my outputted file I get

# PSI Format 1.0
#
# column [0] = "x"
# column [1] = "y"
# column [2] = "z"
# column [3] = "Energy"
# column [4] = "Id"
# type[3] = byte

-52.387596 61.65918 -2.2772269 0 1
-52.341648 61.52145 -2.2433131 0 2
-52.383675 61.594273 -2.273051 0 3
-52.337238 61.465927 -2.241447 0 4
-52.379589 61.535492 -2.2739329 0 5
-52.371269 61.574524 -2.207932 0 6
-52.373951 61.478222 -2.2791619 0 7

As you can see the numbers are not the same....

Here's my output file, making the one change above.

Code:

#PSI Format 1.0
#
# column [0] = "x"
# column [1] = "y"
# column [2] = "z"
# column [3] = "Energy"
# column [4] = "Id"
# type[3] = byte

-52.387596 61.65918 -2.277227 0 0
-52.341648 61.52145 -2.243313 0 1
-52.341648 61.52145 -2.243313 0 2

>So is there some rounding that goes on in the debugger? I have a watch on x, y, z and they are always rounded?

I never use a debugger, maybe someone knows why the Debugger rounds.

Well, you can do this if you want 6 digits after the decimal:

Code:

			foutput << fixed << setprecision(6) << x  << " " << y << " " << z << " " << 0 << " " << index << endl ;

I believe it will print properly, as long as your input contains six digits or less after the decimal. Same technique as Manofsteel showed.

Floating point numbers don't necessarily have an exact binary representaion so that is probably why you are losing some precision. If you need precision try a BinaryCoded Decimal library that will maintain the precision.

[edit]
Here is an MSDN article that explains.
http://support.microsoft.com/default...NoWebContent=1