Корректное округление чисел

Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

{ 
  The function Round of the Delphi doesn"t work 
  like it is usually expected. 
  The odd numbera are rounded down and the even numbers up. 

  Die Round Funktion in Delphi gibt normalerweise nicht 
  die erwartete Zahl zurьck. 
  Die ungeraden Zahlen werden abgerundet, die geraden aufgerundet 

  Example/ Beispiel: 

  x:= Round(17.5) = x = 18 

  x:= Round(12.5) = x = 12 
}

 function DoRound(const X: Extended): Int64;
 begin
   Result := 0;
   if X0 then
     Result := trunc(X + 0.5);
   if Xthen
     Result := trunc(X - 0.5);
 end;


 procedure TForm1.Button1Click(Sender: TObject);
 begin
   ShowMessage(FormatFloat("0.00", DoRound(17.5)));  // - 18 
  ShowMessage(FormatFloat("0.00", DoRound(12.5)));  // - 13 

  //This rounds every value to 0.05 steps 
  //Rundet in 0.05 Schritten 
  ShowMessage(FormatFloat("0.00", Round(17.22 / 0.05) * 0.05)); // - 17.20 
end;


 {***Another function:***}

 function RoundUp(Value: Extended): Int64;
   procedure Set8087CW(NewCW: Word);
   asm
          MOV     Default8087CW,AX
          FNCLEX
          FLDCW   Default8087CW
  end;
 const
   RoundUpCW = $1B32;
 var
   OldCW: Word;
 begin
   OldCW := Default8087CW;
   try
     Set8087CW(RoundUpCW);
     Result := Round(Value);
   finally
     Set8087CW(OldCW);
   end;
 end;

 procedure TForm1.Button2Click(Sender: TObject);
 begin
   ShowMessage(FormatFloat("0.00", RoundUp(19.32)));  // - 19 
end;

Обсудить статью на форуме