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List:       kde-devel
Subject:    Re: Open Bugs in 3.2
From:       Joachim Eibl <joachim.eibl () gmx ! de>
Date:       2004-01-11 23:32:02
Message-ID: 200401120032.02805.joachim.eibl () gmx ! de
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> #include <stdio.h>
> int main()
> {
>   long double a=49.84;
>   long double b=33.52;
>   long double c=a+b;
>   printf("%2.2llf + %2.2llf = %2.14llf\n",a,b,c);
> }

This little program contains a little surprise because you assign a double 
constant to a long double variable.

Check this on your machine.
  long double a=49.84;       // double constant
  printf("%2.30llf\n",a);        // 49.840000000000003410605131648481
  long double a1=49.84L;   // long double constant
  printf("%2.30llf\n",a1);      // 49.840000000000000000138777878078

This just illustrates how tricky it can be. 
BTW: There is no real general solution. You might just settle for a compromise 
like showing fewer digits. But it won't help you when you start subtracting 
almost equal numbers like: 1000.0000 - 1000.0001 etc. 

Cheers,
Joachim
 
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