Skipped footnote numbers in math mode

Question

I want to call footnotes in (self-explanatory) equations, so I use \footnotemark and \footnotetext, but the footnote numbering is going wrong. Numbers skip from 1 to 3 (when I'd want a 2), and when I try to addtocounter footnote -1, it doesn't skip anymore, and doesn't increment at all.

Why is that so, and how to get consecutive numbers ?

MWE :

\documentclass[12pt]{report}
\usepackage{amsmath}
\begin{document}

$1^{st}$ footnote call\footnote{some footnote}.
\[a \xrightarrow{2^{nd}\footnotemark} a\]
\footnotetext{$\leftarrow$ this should be footnote 2}

\[a \xrightarrow{3^{rd}\footnotemark} a\]
\footnotetext{$\leftarrow$ this should be footnote 3}

\[a \xrightarrow{4^{th}\addtocounter{footnote}{-1}\footnotemark} a\]
\footnotetext{$\leftarrow$ following the pattern, I'd expect this to be 7 without fix, 6 once fixed. But 5??}
\end{document}

score 2 · Accepted Answer · edited Apr 13 '17 at 12:35

2

Don't do it. Superscripts in math have mathematical meaning and you are confusing the reader with such footnote marks. See also https://tex.stackexchange.com/a/155481/2388.

Beside this: Quite a number of math expressions are processed more than once and so change counters. In your case the problem is the arrow, so you should reset the footnote counter before it.

\documentclass[12pt]{report}
\usepackage{amsmath}
\begin{document}

$1^{st}$ footnote call\footnote{some footnote}.
\[a \addtocounter{footnote}{-1}\xrightarrow{2^{nd}\footnotemark} \]
\footnotetext{$\leftarrow$ this should be footnote 2}

\end{document}

edited Apr 13 '17 at 12:35

Community

1

answered Oct 26 '16 at 08:05

Ulrike Fischer

327,261

It's not really math-mode, it really is text over the arrow. I did read, and link to, the same answer as you mention. That works, and I maybe I'll look further into "processed several times", I understand that the counter update had been counted twice, that makes sense now ; many thanks ! – Nikana Reklawyks Oct 26 '16 at 17:34

score 0 · Answer 2 · answered Oct 26 '16 at 11:41

Be kind to your readers and don't inflict them footnotes in math mode.

Just to show it's possible, here it is.

\documentclass[12pt]{report}
\usepackage{amsmath}

\makeatletter
\def\ext@arrow#1#2#3#4#5#6#7{%
  \mathrel{\mathop{%
    \let\mathfootnotemark\fake@footnotemark
    \setbox\z@\hbox{#5\displaystyle}%
    \setbox\tw@\vbox{\m@th
      \hbox{$\scriptstyle\mkern#3mu{#6}\mkern#4mu$}%
      \hbox{$\scriptstyle\mkern#3mu{#7}\mkern#4mu$}%
      \copy\z@
    }%
    \hbox to\wd\tw@{\unhbox\z@}}%
  \limits
    \@ifnotempty{#7}{^{\if0#1\else\mkern#1mu\fi
                       #7\if0#2\else\mkern#2mu\fi}}%
    \@ifnotempty{#6}{_{\if0#1\else\mkern#1mu\fi
                       #6\if0#2\else\mkern#2mu\fi}}}%
}
\newcommand{\mathfootnotemark}{%
  \ifmeasuring@
    \fake@footnotemark
  \else
    \footnotemark
  \fi
}
\newcommand{\fake@footnotemark}{%
  \textsuperscript{\the\numexpr\value{footnote}+1\relax}%
}
\makeatother

\begin{document}

$1^{st}$ footnote call\footnote{some footnote}.
\[a \xrightarrow{2^{nd}\mathfootnotemark} a\]
\footnotetext{$\leftarrow$ this should be footnote 2}%
text
\[a \xrightarrow{3^{rd}\mathfootnotemark} a\]
\footnotetext{$\leftarrow$ this should be footnote 3}%
text
\[a \xrightarrow{4^{th}\mathfootnotemark} a\]
\footnotetext{$\leftarrow$ this should be footnote 4}%
text
\begin{align}
a & \xrightarrow{5^{th}\mathfootnotemark} a \\
b & \xrightarrow{xxxx} b
\end{align}
\footnotetext{$\leftarrow$ this should be footnote 5}%
text
\end{document}

Skipped footnote numbers in math mode

2 Answers2