1. Is there any general way besides restarting the kernel to make sure that nothing I've done earlier in a session will affect code I want to run now?

One book suggested running Clear["Global'*"] but this did not protect me from the problem illustrated below.

  1. To verify whether I need to do something like restart the kernel, is there a way to get a list of all user definitions or assignments that are still in effect?

Background: I ran into a problem because I set y' equal to a+b*y, tried to clear y, found that y' was not a symbol, and mistakenly thought that this assignment was no longer in effect even though it was. Eventually, I discovered that I had to use Remove[y] to undo this assignment.

In[1]:= y' = a + b*y
Out[1]= a + b y
In[2]:= Clear[y]

In[5]:= Clear[y']

And getting an error

In[5]:= Clear::ssym: y^[Prime] is not a symbol or a string. >>

In[6]:= Information[y']

During evaluation of In[6]:= Information::ssym: y^[Prime] is not a symbol or a valid string pattern. >>

Out[6]= Information[Derivative[1][y]]

In[7]:= ?y'

During evaluation of In[7]:= Information::nomatch: No symbol matching y' found. >>

(* Looks like there is no trace of my assignment from line 1. And yet ... *) 

In[8]:= y'
Out[8]= a + b y
In[9]:= Remove[y']

During evaluation of In[9]:= Remove::ssym: y^[Prime] is not a symbol. >>

In[10]:= Remove[y]

In[11]:= y'
Out[11]= Derivative[1][y]
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    – user9660
    Dec 15, 2014 at 16:09
  • $\begingroup$ @Lou, please edit the link. it is giving the current question. $\endgroup$ Dec 15, 2014 at 16:23
  • 1
    $\begingroup$ Have you seen this How to Clear variables with apostrophe? $\endgroup$
    – user9660
    Dec 15, 2014 at 16:25
  • $\begingroup$ @Algohi, thanks for the hint, very thoughtful of you. $\endgroup$
    – user9660
    Dec 15, 2014 at 16:26
  • 2
    $\begingroup$ @Mr.Wizard even that may not be enough. Remember that Manipulates with the SaveDefinition option set to true may inject definitions into a session as soon as the Manipulates come into view. $\endgroup$ Dec 15, 2014 at 21:40

1 Answer 1


I'm not sure if this will help, but I use

Remove["Global `*"]

(note that the first quotation is the left quotation mark associated with the tilde key, U.S. keyboard, not the single quote associated with the double quotation key.


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