force the mod operator to return non-negative int

				
!**************************************
! Name: force the mod operator to return non-negative int
! Description:Given integers A and B, A mod B doesn't always return a value between zero and B when A or B are negative.
! By: Don Rowlett
!
! Inputs:Two integers: non-zero A and positive B.
!
! Returns:a non-negative integer less than B
!
! Assumes:mod is usually used to extract the remainder in a division. This works if both operands are positive.
!
! Side Effects:nothing significant
!
!This code is copyrighted and has! limited warranties.Please see http://www.Planet-Source-Code.com/vb/scripts/ShowCode.asp?txtCodeId=1676&lngWId=7!for details.!**************************************

// A mod B ---->> return 0,1,2,...,(B-1)
//
// Integer B is assumed to be 2 or greater.
// !!! This condition is NOT checked. !!!
//
procedure TForm1.Button1Click(Sender: TObject);
var
 a, b, alpha: Integer;
begin
 a:= StrToInt(NumEdit1.Text); b:= StrToInt(NumEdit2.Text);
 if a*b = 0 then begin a:= 10; b:= 3; end; { dummy proof }
 alpha:= a mod b;
 if alpha < 0 then
repeat
 alpha:= alpha + b;
until alpha > -1;
 Label2.Caption:= IntToStr(alpha);
end;