Subject Re: float vs double precision
Author bwc3068
Sounds like i need to change the "float" to "double precision" in the SQL that generates the table then?

--- In, Geoff Worboys <geoff@...> wrote:
> Hi Kelly,
> > IF I input "1.23" into the Double Precision field and then
> > tab off of it, it reads: 1.23.
> > If I input "1.23" into the Float field and then tab off of
> > it, it reads:
> > 1.23000001907349
> > Any idea why the "float" field display incorrectly after the
> > value get's placed into the query?
> The reason is fairly simple - Delphi is not very good with
> single ("float") data types. Many of it's function are not
> overloaded to single (or even double), instead the value is
> automatically cast up to extended with its supposed 18+
> digits of significance.
> FloatToStr is one such example, math.RoundTo and math.
> SimpleRoundTo are additional examples (as are RoundNear etc
> supplied with IBO).
> NOTE: Beware of math.SimpleRoundTo - I recently discovered
> that the implementation changed sometime between Delphi6 and
> Delphi2010 and it is no longer asymmetric as described in the
> supplied help files. I've written to Embarcadero but have
> not received any response.
> You can work around the problem by implement specific to-str
> conversions that limit the output digits (which is usually a
> good idea anyway) but it is very difficult to prevent unwanted
> surprises arising from the use of single-precision fp.
> My conclusion, from back in Delphi5 days and not changed since,
> is that the float/single data-type, which is never very useful,
> is pretty close to completely useless in Delphi. As a result
> things like percentages, which technically only "needed" float
> I have implemented as double anyway.
> --
> Geoff Worboys
> Telesis Computing