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
    Commented Mar 25, 2014 at 8:33

2 Answers 2


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. Commented Mar 25, 2014 at 8:40
  • Also, as suggested above, I am now using \textbf instead of \bf. Commented Mar 25, 2014 at 8:40
  • see myedited answer.
    – user2478
    Commented Mar 25, 2014 at 8:46
  • It works by putting {} around the second argument. Commented Mar 25, 2014 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
    Commented Mar 25, 2014 at 8:54

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