[2263] XML dump of DOUBLE rounds values

[Charles Yeomans]

On Mar 26, 2007, at 5:58 PM, Ruslan Zasukhin wrote:

> Hi All,
>
> Well, after some play I have found not nice things.
>
>
> -------------
> * we have in C/C++ language some DOUBLE value
>
>     double dv = 10149.25;
>
>
> -------------
> * we do standard C call
>
>         printf( buff, "%G", dv );
>
> And we get
>     buff = "10149.2" on MAC, XCODE
>     buff = "10149.3" on WIN, MS Visual
>
> -------------
> * IF to increase precision
>         printf( buff, "%.40G", dv );
>
>  We get something as
>
>     buff = "10149.2500036346345676547567567785678"
>                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^ unexpected trail.
>
>
> --------------
> RESUME:
>
>     there is no technical way convert any possible DOUBLE VALUE
>     into string accurately.
>
>
> This is why I again want to point. If you need EXACT storage of  
> numbers,
> DO NOT use DOUBLE/FLOAT type.


Why not dump doubles by casting them to an 8-byte string, then  
base-64-encoding that?

Charles Yeomans