The problem is that what you see is not what you think it is. When you call for instance
Inactivate[Integrate[1/(1 + x), x]]
then every operation (every function-call f[x,y,z]
in the FullForm
) is converted to Inactive[f][x,y,z]
without evaluating anything. What makes Inactivate
neat is that for many expression Inactive[func][args]
has certain FormatValues
attached which make it look like you had the original expression. Therefore, if you evaluate the above line, you will see the following on screen
![Mathematica graphics](http://i.stack.imgur.com/h3NUP.png)
but in fact, this is only the representation in your standard output form. When you explicitly ask for the InputForm
you see what it really is
Inactivate[Integrate[Sin[x],x]]//InputForm
(* Inactive[Integrate][Inactive[Sin][x], x] *)
If you look at FormatValues[Inactive]
you see some of the rules that are used to build the box-representation you see on screen. If you want you can do
Unprotect[Inactive];
ClearAll[Inactive];
SetAttributes[Inactive, HoldFirst];
and then call the first line again and you see that all the fancy representation is gone. Unfortunately, this does not work for the most basic operations like Times
, Plus
etc. Their formatting rules seem to be built-in and so they still have the box-form with the *
you don't like
ToBoxes[Inactivate[x y]]
(* RowBox[{x,TagBox[*,InactiveToken,BaseStyle->Inactive,SyntaxForm->*,Editable->False,Selectable->False],y}] *)
Therefore, the short answer to your question is: the slightly highlighted *
sign in an inactivated x y
is show to indicate that the operator is not active.