Randomly sorting TMemo, code bug? 1

[KempCGDR]

I have the following code:

      Randomize;
      For i := 1 to frmMain.memOrig.Lines.Count do
      begin
         RandNo := Random(frmMain.memOrig.Lines.Count)+1;
         frmMain.memNew.Lines.Add(frmMain.memOrig.Lines[RandNo]);
         frmMain.memOrig.Lines.Delete(RandNo);
      end;

It is meant to put the contents of memOrig into memNew in a random order. For some reason that I can't see, there is are always some items left in memOrig (usually two, but not always). I tried changing the For statement to a fixed number (the number of items in it), with the same result. I've got to be missing something obvious as this is only a small, simple piece of code. Can anyone spot it?

 

[KempCGDR]

Now changed for ease of reading, same basic code:

      Randomize;
      With frmMain do
      begin
         For i := 1 to memOrig.Lines.Count do
         begin
            RandNo := Random(memOrig.Lines.Count)+1;
            memNew.Lines.Add(memOrig.Lines[RandNo]);
            memOrig.Lines.Delete(RandNo);
         end;
      end;

 

[Zathras]

Try changing the first statement after the begin to:
[blue]

  RandNo := Random(memOrig.Lines.Count - 1);

[/color]
That seems to work for me.

 

[KempCGDR]

Doh! The number of lines is 60, but the numbering will be 0 -> 59. I'll try

      Randomize;
      With frmMain do
      begin
         For i := 1 to memOrig.Lines.Count do
         begin
            RandNo := Random(memOrig.Lines.Count)+1;
            memNew.Lines.Add(memOrig.Lines[RandNo-1]);
            memOrig.Lines.Delete(RandNo-1);
         end;
      end;

and get back.

 

[KempCGDR]

Works! Thanks for triggering that memory, and it can be obviously simplified now by dropping the +1 and -1 on the various bits. Thanks again.