I'm gonna typeset a NOT \ll using the method explained here by @Leo Liu.

This code snippet that uses the minimum required packages perfectly works:




(\forall \pi_{i},\pi_{j} \in \mathcal{P}) [\pi_{i} \centernot\ll \pi_{j} \wedge \pi_{j} \centernot\ll \pi_{i}].


But when I use the method in my main file including many other packages, an error is thrown about Missing $ inserted!


\usepackage[top=2cm, left = 2cm, right = 2cm, bottom = 2cm]{geometry}


(\forall \pi_{i},\pi_{j} \in \mathcal{P}) [\pi_{i} \centernot\ll \pi_{j} \wedge \pi_{j} \centernot\ll \pi_{i}].    % error is here


I guess there is a package conflict.

How can I fix this issue?!

Edit 1:

The error:

Missing $ inserted. ...j} \in \mathcal{P}) [\pi_{i} \centernot\ll

Edit 2:

The conflict is with fdsymbol package.

  • Comment out packages until you make the error go away and identify the culprit that way. What else is there to do? I know robotics isn't rocket science, but .... Please provide the complete text of error messages. This will include a line number. Also, try pressing h for more help when you get the error. – cfr Aug 22 '17 at 4:01
  • @cfr: The problem is that I need all of those packages. The question is actually whether or not the issue can be fixed without removing any other packages. – Roboticist Aug 22 '17 at 4:04
  • @cfr: The error message and its location are added to the question. – Roboticist Aug 22 '17 at 4:06
  • The point is that you can tell us where the conflict is. We don't need a full list of everything you're loading. Find the conflict. See if the packages' manuals address it. If not, post a question about that conflict. This is all anybody can do unless they happen to know off-hand that X and Y conflict. It is just a mechanical diagnostic: you can do it as well or better than anyone else. – cfr Aug 22 '17 at 4:06
  • 1
    centernot clash with fdsymbol. instead \centernot\ll try if \nll from fdsymbol gives satisfactory result for you and if, removecenternot package from preamble. – Zarko Aug 22 '17 at 4:33

Package fdsymbol provides a wide range of symbols, in which many negated symbols from amssymb are available. Thus, package centernot is actually superfluous, and the clash will also be resolved.

I suggest using \nll from package fdsymbol instead of \centernot\ll.


Package centernot assumes the original \not, which is a simple relational symbol. Package fdsymbol redefines \not as macro with one argument.

The patch in the following example redefines \@centernot to allow \not being a macro with one argument:



% Patch centernot to support \not as macro with argument.
  \errmessage{Patching \noexpand\@centernot failed.}%

    (\forall \pi_{i},\pi_{j} \in \mathcal{P}) [\pi_{i} \centernot\ll \pi_{j}
    \wedge \pi_{j} \centernot\ll \pi_{i}].


Of course, using a real negated symbol as \nll of package fdsymbol as in Zarko's answer is the preferred solution.

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