How can I define a macro with literal square brackets in the body?

Question

The following macro works correctly for enclosing an expression in parenthesis.

\def\group#1{\left ( #1 \right )}

I want to write the equivalent macro for enclosing an expression in square brackets. I have tried the following macro with and without backslash-escaping the the square brackets, but both give errors.

\def\bgroup#1{\left [ #1 \right ] }

How can I define a macro with the desired expansion?

\bgroup is a name used within the LaTeX kernel: did you try with a different name? (\newcommand rather than \def would tell you this.) — Joseph Wright, Oct 29 '13 at 20:24
Changing the name fixed it. That error message was really cryptic! Thank you. — merlin2011, Oct 29 '13 at 20:33
I could delete the question, but if you want to write your comment as an answer, I'll accept it and we can leave it as a reference in case somebody else happened to use def and the name bgroup together. — merlin2011, Oct 29 '13 at 20:35
A few information about \bgroup, \begingroup and {: When should one use \begingroup instead of \bgroup? — Qrrbrbirlbel, Oct 29 '13 at 20:46
@merlin2011 Try doing \def\fi{whatever} in the preamble. The error message will be much more cryptic. Use \newcommand unless you know precisely what you're doing. Redefining “taken” commands is surely possible, but with great care and not just to glob their original meaning. — egreg, Oct 29 '13 at 21:51

score 9 · Accepted Answer · answered Oct 29 '13 at 20:48

The command \bgroup is used by the LaTeX kernel (and indeed by plain TeX) for low-level operations: as such it is 'reserved'. Thus the problem is not [ and ] in the command but rather the choice of \bgroup as the name for it. If you use \newcommand rather than \def you'll see an informative error message indicating that \bgroup is 'taken'.

How can I define a macro with literal square brackets in the body?

1 Answers1