CODEWITHSUNDEEP
delphimathintegermodulo
Jeff
Jeff

Reputation: 12163

Using "mod" operator

I am trying to display whenever I need to do a certain action in my for loop every 300th iteration (makes sense?)

Here is in code what I want to do, but not the way I want to do it:

for I := 0 to 2000 do
  Begin
   if I = 300 then
   DoAnAction;

   if I = 600 then
   DoAnAction

   if I = 900 then
   DoAnAction

   if I = 1200 ......... Same action all over, but I don't want to check all those conditions!
  End;

So I have been told to use the mod operator, and this is how I do it:

for I := 0 to 2000 do
 Begin
  if I mod 300 = 299 then
  DoAnAction;
 End;

However, the results using the above snippet would do the action at 299, 599, 899 ....

How can I make it do it at 300, 600, 900 ...... using the Mod operator? (And doing if I mod 300 = 300 did not work)

Thanks!

Upvotes: 3

Views: 17975

Answers (4)

Kromster
Kromster

Reputation: 7397

for I := 0 to 2000 do
 Begin
  if (I mod 300 = 0) and (I > 0) then
    DoAnAction;
 End;

Though your previous version does makes sense too, I=299 is the 300th pass ;)

EDIT: I mod 300 = 300 would not work because mod operator returns the remainder of devision, which is by definition will be in range 0..299

Upvotes: 10

Ken White
Ken White

Reputation: 125688

Use this:

if i mod 300 = 0

The modulus operator returns the remainder of a division.

Here's an example to help you out. Drop a TMemo on a blank new form, and put this in the FormCreate evemt:

procedure TForm1.FormCreate(Sender: TObject);
var
  i: Integer;
const
  Output = 'i mod %d = %d';
begin
  Memo1.Clear;
  for i := 0 to 10 do
    Memo1.Lines.Add(Format(Output, [i, i mod 5]));
end;

Run it, and look at the output in the memo.

Upvotes: 4

NawaMan
NawaMan

Reputation: 25687

Try (I <> 0) AND ((I mod 300) = 0).

Upvotes: 0

Femaref
Femaref

Reputation: 61437

The mod operator returns the rest of the division. So if you want to do it every 300th iteration, use i mod 300 = 0.

I mod 300 = 300 doesn't make sense, as there can't be a division by 300 leaving a rest of 300.

Upvotes: 4

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