double data type

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double data type

 
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  #1
Nov 9th, 2008
When i use a variable type double the value e.g 345624.769123 rounded to 345625
but when i take 5 digits before decimal i.e 34562.4769123 then it shows 34562.5

Please explain Why?

Thanks
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Re: double data type

 
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Nov 9th, 2008
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Originally Posted by jugnu View Post
When i use a variable type double the value e.g 345624.769123 rounded to 345625
but when i take 5 digits before decimal i.e 34562.4769123 then it shows 34562.5
Please explain Why?
Thanks
Please explain where and when?
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Re: double data type

 
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Nov 9th, 2008
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Originally Posted by ArkM View Post
Please explain where and when?
#include<iostream>
#include <conio.h>

using std::cout;
using std::cin;

main()
{
double x=345624.769123;
cout<<"x=";
cout << x;
getch();
}
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Re: double data type

 
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  #4
Nov 9th, 2008
The 5 digits before have nothing to do with it. When your system is rounding to tenths then xxxx.47.. is rounded to xxxx.5 just as xxxxxx.79.. is rounded to xxxxxx+1.
Read also : http://en.wikipedia.org/wiki/Rounding
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Re: double data type

 
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  #5
Nov 9th, 2008
It's simply default precision of stream output. Don't worry, double type always keeps ~16 significant digits...
Use setprecision manipulator from <iomanip> to set another output precision:
C++ Syntax (Toggle Plain Text) 
  1. #include <iomanip>
  2. double x = ......;
  3. ...
  4. for (int n = 0; n < 17; ++n)
  5.     cout << setprecision(n) << x << endl;
Try this and see what happens...
Last edited by ArkM; Nov 9th, 2008 at 3:52 pm.
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