Re: Float to String

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 08 Nov 2004 18:06:04 +0100, Pascal Obry wrote:

> I was wondering if there is a way to save a float into a string and read it
> back without loosing precision ?
> 
> I tried something like:
> 
>    F_Str : String (1 .. Float'Base'Digits);
> 
>    Float_Text_IO.Put (F_Str, My_Float, Aft => Float'Base'Digits);
> 
> But this is not enough... Ideas ?

There is no any portable way to do so. Floating-point numbers are intended
to be imprecise. Normally the application domain should determine the
required accuracy. It is definitely possible to maintain that accuracy
during I/O conversions. What is impossible and meaningless, is to try to
define the *application-specific* accuracy as "the ultimate accuracy of
Float on this concrete machine for this concrete compiler". Another
question is asymptotic behavior of repeated forth and back conversions. I
would not expect that its error is unbounded, however ARM is silent about
that.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de