General ⇒ undefining (not redefining) a "\newcommand"

[Curious George]

When writing messy equations, I frequently use \newcommand to reduce typing, reduce errors, and improve consistency. Here is an example from a current paper:

\newcommand{\NN}[1]{\sqrt{\sin^2 {#1}-CC}}

I would like to "undefine" the macro at the end of the section where it is used. Then, if it is accidentally typed in a later section where it doesn't belong, LaTeX would halt and give an error.

Of course, it would be possible to use something like

\renewcommand{\NN}{\mbox{ERROR}}

but, besides being somewhat inelegant, this would require being able to spot the error message in the finished paper. My preference would be the LaTex processor itself to detect the error.

So, my question: is there a way to undefine a \newcommand, so that any future attempt to use it results in an "Undefined control sequence" error?

Thanks for any assistance.

[sommerfee]

Code: Select all

\let\NN\undefined

should do the trick (at least as long as \undefined is undefined).

[Curious George]

Thank you, sommerfee.

The following

Code: Select all

\documentclass{article}
\begin{document}
\newcommand{\NN}[1]{\sqrt{\sin^2 {#1}-CC}}
$$ A = \frac{\sin\alpha\cos a}{\NN{x}} $$
\let\NN\undefined
$$ A = \frac{\sin\alpha\cos a}{\NN{x}} $$
\end{document}

fails, as desired, with the message

Code: Select all

! Undefined control sequence.
<argument> \NN
               {x}
l.8 $$ A = \frac{\sin\alpha\cos a}{\NN{x}}
                                           $$

Changing the "\let" statement to

Code: Select all

\renewcommand{\NN}{\undefined}

also fails, with a slightly different message:

Code: Select all

! Undefined control sequence.
\NN ->\undefined
                 
l.9 $$ A = \frac{\sin\alpha\cos a}{\NN{x}}
                                           $$

Have a slight preference for the first form, using"\let". On the other hand, "\renewcommand" would help insure that it was really "\NN" that was undefined.

Will mark this thread as solved.

[localghost]

[…] Will mark this thread as solved.

Topics are not marked as solved by tagging them. They are marked correspondingly by accepting the answer that led to the solution.

A remark not related to the problem. Do not use the TeX syntax $$ … $$ for unnumbered displayed equations. It causes unwanted side effects (alignment, spacing). Use the LaTeX syntax \[ … \] instead. Perhaps you should read about "deadly sins" in l2tabu.


Thorsten