I came across a problem when typing my report. I do not know how to fix this. The problem is as follows:

I have two custom commands defined like this:

\newcommand{\slr}[1][n]{\ensuremath{{\bf SL}(#1,\mathbb{R})}}

\newcommand{\lie}[1][G]{\ensuremath{{\bf L}(#1)}}

So that the first command gives an output like ${\bf SL}(n,\mathbb{R})$ and the second command gives the output like ${\bf L}(G)$. Here $n$ and $G$ are respectively the default arguments.

Now when I use these two commands together, I hope to get

$${\bf L}({\bf SL}(2,\mathbb{R}))$$

However, for some reason what I am getting is

$$ {\bf L}({\bf SL}(2),\mathbb{R})$$

Any ideas of what is going on here?

  • In LaTeX, don't use \bf; use \bfseries or \textbf{...} or \mathbf{...}. – jub0bs Mar 25 '14 at 8:33

The problem in \lie[\slr[2]] is that the optional argument to \lie is taken to be \slr[2. You can solve the issue with xparse:




Here it is: $\lie[\slr]$

With optional argument: $\lie[\slr[2]]$

enter image description here

I removed \ensuremath as I believe that you gain nothing from using \lie in text rather than $\lie$; to the contrary, I firmly believe that the latter form is much better, because math is always treated as math.


I cannot see it:



\[ {\bf L}({\bf SL}(2,\mathbb{R})) \]

\[ \lie[{\slr[2]}] \]

\[ \slr[\lie] \]


enter image description here

You have to put the optional argument into braces: [{\slr[2]}]

  • I am still getting the same problem. I am using the book class, if that helps. – Vishal Gupta Mar 25 '14 at 8:40
  • Also, as suggested above, I am now using \textbf instead of \bf. – Vishal Gupta Mar 25 '14 at 8:40
  • see myedited answer. – user2478 Mar 25 '14 at 8:46
  • It works by putting {} around the second argument. – Vishal Gupta Mar 25 '14 at 8:51
  • 1
    [\slr[2]] takes the first ] as closing brace for the first [ and not for the second one, because [ looks only for a following ] – user2478 Mar 25 '14 at 8:54

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.