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Rounding up problem

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Join Date: Dec 2007

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Quakes

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Rounding up problem

Mar 4th, 2008

I'm attempting to read lines of a file and store the contents of the line in an object.

This is an example line (x,y,z co-ordinates) :

-12.852222 32.548111 -934.306681

My problem is that my program is rounding these numbers up and I need absolute precision. Having read one line, storing the numbers in the object and printing out the values to make sure they are correct they now look like this:

X: -12.8522 Y: 32.5481 Z: -934.307

This is probably something to do with the types I'm using. The variables are declared as doubles in the object. I've also tried floats, which still gives the same problems.

If you want to see any of my code, please just ask.

Thanks

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Join Date: Dec 2006

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vijayan121 vijayan121 is offline

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Re: Rounding up problem

Mar 4th, 2008

> printing out the values to make sure they are correct they now look like this ...
the initial default precision for a stream is 6. to print out more decimal digits, do something like

 Help with Code Tags 
 C++ Syntax (Toggle Plain Text) 
std::cout << std::fixed << std::setprecision(8) 
          // 8 digits *after* decimal point
          << value ;
std::cout << std::fixed << std::setprecision(8) 
          // 8 digits *after* decimal point
          << value ;

> I need absolute precision.
you will not get absolute precision with floating point values.
if the precision of a long double is not sufficient, you would either use integral types (numerator,denominator) or use a high precision arithmetic library.

Last edited by vijayan121; Mar 4th, 2008 at 3:21 pm.