[Tex/LaTex] angle brackets in math and text mode

math-modetext-mode

I use \textlangle and \textrangle in a command

\newcommand{\qdist}[1]{\textlangle#1\textrangle}

which is used in math and text mode. In math mode, I get the error message

LaTeX Warning: Command \textrangle invalid in math mode on input line 952.

what similar symbol could be used in both modes? I use Lualatex.

the MWE

\documentclass[msmallroyalvopaper
    ]{memoir}

\newcommand{\qdist}[1]{\textlangle#1\textrangle}

\begin{document}

text with \qdist{word} 

and some math 
\[   a = \qdist{symbol} \]
The multiple applications of a GIS can be summarized in three prototypical situations:

more text 

\end{document}

Best Answer

You could incorporate an \ifmmode conditional, to use \langle and \rangle in math mode and \textlangle and \textrangle in text mode.

This approach works with pdfLaTeX, LuaLaTeX, and XeLaTeX.

\documentclass{memoir}
\usepackage{textcomp} % for \textlangle and \textrangle macros
\newcommand{\qdist}[1]{\ifmmode\langle#1\rangle\else\textlangle#1\textrangle\fi}
\begin{document}
\qdist{word}, $\qdist{symbol}$
\end{document}

Addendum -- As @egreg has pointed out in a comment and in his separate answer, using \newcommand to create the \qdist macro, as is done above, can run into trouble. It's necessary to use \DeclareRobustCommand instead of \newcommand.

Related Solutions

[Tex/LaTex] Correct usage of math inside text

You gain nothing, in my opinion, in having two different commands: just say

This is some text with \(\sabc\) and a formula \(\sabc+x\).

If you want to save some keystrokes, use

This is some text with $\sabc$ and a formula $\sabc+x$.

Math should be always math. With two commands you'll almost surely end up with using the wrong one and editing will be painful.

A different approach might be to say

\usepackage{xspace}
\newcommand{\sabc}{\ensuremath{A_{\mathrm{b}}^c}\xspace}

using \sabc both in text and math. But with the former approach you'll get the benefit of correct syntax highlighting, if your editor does it.

[Tex/LaTex] Correct usage of \ifmmode

At the start of an alignment cell TeX expands macros looking for \omit (\multicolumn) the math start in the cell template has not been added at this point so \ifmmode is always false.

You need to put \relax in front of it to kill the pre-scan for \omit or make the command containing this construct be robust so it doesn't expand in this context (using LaTeX \DeclareRobustCommand or eTeX \protected)

To show the various approaches, this plain eTeX file

\def\foo{\ifmmode \phi\else fi\fi}
\protected\def\pfoo{\ifmmode \phi\else fi\fi}
\def\rfoo{\relax\ifmmode \phi\else fi\fi}

\halign{#)&$#$\hfill&\quad dif#cult\cr
0&\omit $\phi$\hfill&\omit \quad dif{f}icult\cr
1&\omit $\phi$\hfill&\omit \quad difficult\cr
2&\foo&\foo\cr
3&\pfoo&\pfoo\cr
4&\rfoo&\rfoo\cr
}


\bye

produces

enter image description here

(1) is what you want.

(0) loses the ffi ligature.

(2) the non robust unprotected command gets the ffi ligature but messes up the if math test.

(3) the etex \protected macro does the same as (1).

(4) using \relax (which would be the same as using \DeclareRobustCommand in LaTeX in this context) gets the math test correct but loses the ffi ligature.

Best Answer

Related Solutions

[Tex/LaTex] Correct usage of math inside text

[Tex/LaTex] Correct usage of \ifmmode

Related Question