Limits of symbolic sums/products in display-style math

[simon-pfahler]

When a limit of a \sum or a \product is changed in display-style math, latexdiff shows the limits as if they were set in an inline-math environment.

Example:

old.tex

\documentclass{article}

\begin{document}
\begin{equation}
    \sum_{n=0}^\infty \frac{1}{n^2}=\frac{\pi^2}{6}
\end{equation}
\end{document}

new.tex

\documentclass{article}

\begin{document}
\begin{equation}
    \sum_{n=1}^\infty \frac{1}{n^2}=\frac{\pi^2}{6}
\end{equation}
\end{document}

The resulting diff.tex obtained from running latexdiff old.tex new.tex > diff.tex is:

diff.tex

\documentclass{article}
%DIF LATEXDIFF DIFFERENCE FILE
%DIF DEL old.tex   Fri May 17 08:37:47 2024
%DIF ADD new.tex   Fri May 17 08:38:43 2024
%DIF PREAMBLE EXTENSION ADDED BY LATEXDIFF
%DIF UNDERLINE PREAMBLE %DIF PREAMBLE
\RequirePackage[normalem]{ulem} %DIF PREAMBLE
\RequirePackage{color}\definecolor{RED}{rgb}{1,0,0}\definecolor{BLUE}{rgb}{0,0,1} %DIF PREAMBLE
\providecommand{\DIFadd}[1]{{\protect\color{blue}\uwave{#1}}} %DIF PREAMBLE
\providecommand{\DIFdel}[1]{{\protect\color{red}\sout{#1}}}                      %DIF PREAMBLE
%DIF SAFE PREAMBLE %DIF PREAMBLE
\providecommand{\DIFaddbegin}{} %DIF PREAMBLE
\providecommand{\DIFaddend}{} %DIF PREAMBLE
\providecommand{\DIFdelbegin}{} %DIF PREAMBLE
\providecommand{\DIFdelend}{} %DIF PREAMBLE
\providecommand{\DIFmodbegin}{} %DIF PREAMBLE
\providecommand{\DIFmodend}{} %DIF PREAMBLE
%DIF FLOATSAFE PREAMBLE %DIF PREAMBLE
\providecommand{\DIFaddFL}[1]{\DIFadd{#1}} %DIF PREAMBLE
\providecommand{\DIFdelFL}[1]{\DIFdel{#1}} %DIF PREAMBLE
\providecommand{\DIFaddbeginFL}{} %DIF PREAMBLE
\providecommand{\DIFaddendFL}{} %DIF PREAMBLE
\providecommand{\DIFdelbeginFL}{} %DIF PREAMBLE
\providecommand{\DIFdelendFL}{} %DIF PREAMBLE
%DIF COLORLISTINGS PREAMBLE %DIF PREAMBLE
\RequirePackage{listings} %DIF PREAMBLE
\RequirePackage{color} %DIF PREAMBLE
\lstdefinelanguage{DIFcode}{ %DIF PREAMBLE
%DIF DIFCODE_UNDERLINE %DIF PREAMBLE
  moredelim=[il][\color{red}\sout]{\%DIF\ <\ }, %DIF PREAMBLE
  moredelim=[il][\color{blue}\uwave]{\%DIF\ >\ } %DIF PREAMBLE
} %DIF PREAMBLE
\lstdefinestyle{DIFverbatimstyle}{ %DIF PREAMBLE
    language=DIFcode, %DIF PREAMBLE
    basicstyle=\ttfamily, %DIF PREAMBLE
    columns=fullflexible, %DIF PREAMBLE
    keepspaces=true %DIF PREAMBLE
} %DIF PREAMBLE
\lstnewenvironment{DIFverbatim}{\lstset{style=DIFverbatimstyle}}{} %DIF PREAMBLE
\lstnewenvironment{DIFverbatim*}{\lstset{style=DIFverbatimstyle,showspaces=true}}{} %DIF PREAMBLE
%DIF END PREAMBLE EXTENSION ADDED BY LATEXDIFF

\begin{document}
\begin{equation}
    \sum\DIFdelbegin \DIFdel{_{n=0}}\DIFdelend \DIFaddbegin \DIFadd{_{n=1}}\DIFaddend ^\infty \frac{1}{n^2}=\frac{\pi^2}{6}
\end{equation}
\end{document}

The \DIF part includes the _{n=0}, instead of just the 0, therefore the subscripts are not directly behind the sum anymore and get displayed in another way.

[ftilmann]

Thanks for the report. According to my assessment, this is difficult to fix without causing problems in other situations in a general way. As marked-up versions are usually for internal use only, I would say minor cosmetic imperfections like this are not a priority.

If somebody wants to have a go I think in postprocessing looking for the pattern \(sum|product) \DIF(add\del)begin) \DIF(add/del){\(SUPER/SUB)SCRIPT|_|^...} and then moving the markup inside the argument of _ or ^ would be the way to go about this.