override public Obj UpdatedAt(long idx, Obj obj)
{
if (idx < 0 | idx >= length)
{
Miscellanea.SoftFail("Invalid sequence index");
}
int offset = Offset();
Obj[] newItems = new Obj[length];
for (int i = 0; i < length; i++)
{
newItems[i] = i == idx ? obj : items[offset + i];
}
return(new MasterSeqObj(newItems));
}
