Align & match length of \rightarrow and \xrightarrow

Question

In the following example, I want to make \rightarrow be the same length as the \xrightarrow, while aligning the two.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
A &\xrightarrow{\mathrm{closed\, loop}} B \\
C &\rightarrow D
\end{split}
\end{equation}
\end{document}

I have found that I can change the length of \rightarrow, using calc's \widthof to get the length right:

\documentclass{article}
\usepackage{amsmath}
\usepackage{calc}
\begin{document}
\begin{equation}
\begin{split}
A &\xrightarrow{\mathrm{closed\, loop}} B \\
C &\parbox{\widthof{$\xrightarrow{\mathrm{closed\, loop}}$}}{\rightarrowfill} D
\end{split}
\end{equation}
\end{document}

But I then lose the alignment of the two arrows (and I am not happy about using $...$ while already in an equation. Is there a way to align these two arrows? Is there a better way to get two arrows of the same length?

score 3 · Accepted Answer · answered Jun 13 '20 at 10:10

3

You only need a \hphantom.

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
A &\xrightarrow{\mathrm{closed\, loop}} B \\
C &\xrightarrow{\hphantom{\mathrm{closed\, loop}}} D
\end{split}
\end{equation}
\end{document}

answered Jun 13 '20 at 10:10

That's exactly what I wanted! I couldn't figure out how to have \xrightarrow not print out the text for the second line, which is why I started messing with \rightarrow. Thank you! – LSchoon Jun 13 '20 at 10:13

ZhiyuanLck · Answer 2 · 2020-06-13T10:33:48.933

This answer is actually the same with @Schrödinger's. I add two commands to make it conveniant to use.

\documentclass{article}
\usepackage{amsmath}
\makeatletter
\newcommand{\firstarrow}[2][default]{
  \expandafter\gdef\csname arrow@content@#1\endcsname{#2}
  \xrightarrow{@nameuse{arrow@content@#1}}
}
\newcommand{\alignarrow}[1][default]{\xrightarrow{\hphantom{@nameuse{arrow@content@#1}}}}
\makeatother
\begin{document}
\begin{equation}
\begin{split}
  A &\firstarrow{\mathrm{closed, loop}} B \
  A &\alignarrow B\
  C &\firstarrow[test]{a_c} D\
  A &\alignarrow B\
  C &\alignarrow[test] D\
\end{split}
\end{equation}
\end{document}

Align & match length of \rightarrow and \xrightarrow

2 Answers2