Mega Code Archive
Rounding
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The Round() function...
As I recall it's a bug in the FPU of the processor itself, not Delphi, the FPU rounds
to the nearest even number in the case of round (<number>.5)
If X is exactly halfway between two whole numbers, the result is always the even
number.
I usually use something like this : (can be easily changed to a function, BTW)
procedure RoundIt(var Amount : Double; Digits : Integer);
var
OneHalf, Power10 : Extended;
begin
If Digits > 19 then Digits := 19;
If Digits < 0 then Digits := 0;
Power10 := Power (10, Digits);
If Amount < 0 then
OneHalf:=-0.5
else
OneHalf:=0.5;
Amount := (Trunc(Amount * Power10 + OneHalf)) / Power10;
end;
Amount is the number you want to round, Digits is the number of decimals you
want to keep.
HTH (hope it's correct as well, cause I use it in several programs...
Bert De Ridder
Analyst/DBA
Nissan Belgium
[note: look also at the Trunc(), Ceil(), and Floor() functions...]
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The way Delphi Round() function works depends on the
value of the 8087 control word. This is set using the
Set8087cw() procedure.
The procedure take one parameter CW: Word, the default
is in the global variable Default8087cw. The bitmasking
etc.. for the is word is documented in Intel
architecture manuals.
To force the Round function to round up you can call the
following during application startup.
Set8087cw($1B32);
You may want to wrap this into your own rounding function
to preserve existing rounding behaviour.
function RoundUp(Value: Extended): Int64;
const
RoundUpCW = $1B32;
var
OldCW: Word;
begin
OldCW := Default8087CW;
try
Set8087(RoundUpCW);
result := Round(Value);
finally
Set8087CW(OldCW);
end;
end;
end;
This information and code is from Delphi in a Nutshell by
Ray Lischner. I have mentioned before how valuable this
book is.
Regards,
Anthony Richardson
Sage Automation
anthony_r@sageautomation.com
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