removeCopyIfIn.md

removeCopyIfIn

A bug was found in the removeCopyIf family of functions, effectively reversing their intended behavior. The following test is now passed:

{
  From the documentation:
    The removeCopy algorithm copies a sequence of items from one location to
    another, removing any matching items as it goes.
    The size of the container doesn’t change; the remove family of functions
    return an iterator positioned at the end of the new sequence. (p. 48)

  A bug was reported by Doug Winsby on 27th Oct 2024 claiming that the
  behavior of removeCopyIfIn routine was reversed: Instead of removing
  objects for which the DTest function returned true, it was including
  them, effectively reversing the intended behavior.

  The test below is passed after adding a "not" to the line
   --   if test(o^) then
}

  // Type DTest
function TTestAlgorithms.IsEvenInteger(const obj : DObject) : Boolean;
begin
  Result := (obj.VInteger MOD 2 = 0);
end;

procedure TTestAlgorithms.TestRemoveCopyIfIn;
var c1, c2 : DArray;
var i : DIterator;
begin
  c1 := DArray.Create;
  try
      // add numbers 1-100 to container
    for var temp := 1 to 100 do
      c1.add([temp]);

    c2 := DArray.Create;
    try
        // copy container to c2 except even numbers
      i := removeCopyIfIn(c1.start, c1.finish, c2.finish, IsEvenInteger);

        // expected results:

        // removeCopyIfIn returns iterator at end of new sequence
      Assert.AreEqual(true, atEnd(i));
        // last odd number in new sequence must be 99
      advanceBy(i, -1);
      Assert.AreEqual(99, getInteger(i));
        // still 100 items in source container
      Assert.AreEqual(100, c1.size);
        // half of the amount in target container
      Assert.AreEqual(50, c2.size);

        // check if all objects in new container are odd numbers
      i := c2.start;
      while(iterateOver(i)) do
      begin
        var n := getInteger(i);
        Assert.IsFalse(n MOD 2 = 0);
      end;

    finally
      c2.Free;
    end;

  finally
  c1.Free;
  end;
end;