! LaTeX Error: Control sequence \sep: already defined

Question

I need merging several research papers compiled using CAS-DC Elsevier template in single .pdf file with bibliography in each research paper and consecutive page numbering across the whole .pdf document. Minimal Working Example at: I need merging several research papers in single .pdf file

I tried confproc, combine, pdfpages and subfiles, docmute packages. Regardless package while compiling main document I always see the same error:

! LaTeX Error: Control sequence \sep: already defined.

In compiled main document I see repetition of Title, Authors, Affilations etc. For instance: In main file in second research paper there are Title, Authors, Affilations, e-mails ORCID etc. from first research paper etc.

It is not about Concatenating I need problem resolution by means of LaTex (MiKTeX, TeXstudio).

All your suggestions will be appreciated. Thank your in advance.

Answer 1

The definition of the keywords environment in cas-common.sty is

\NewDocumentEnvironment { keywords } { O{ Keywords } }
   {
     \tex_global:D \tex_setbox:D \g_stm_key_box = \vtop \bgroup
     \hsize=.25 \textwidth
     \cs_new:Nn \sep: { \par }
     \cs_set_eq:NN \sep \sep:
     \parindent \z@
     A\,R\,T\,I\,C\,L\,E\ \ I\,N\,F\,O \par \skip_vertical:n { -3pt }
     \rule{.25 \textwidth}{.2pt}\par\footnotesize
     \noindent \textit { #1 }:  \par
   }
   { \egroup }

It is difficult to say anything friendly about this code, this is a sort of tex-latex-expl3 pidgin.

In any case the problem is from the (useless) \cs_new:Nn. One should never use this command in environment definitions.

You can avoid the error by redefining the environment (this doesn't make it much nicer, it only avoids the error):

\documentclass[a4paper,fleqn,twoside]{cas-dc}
\ExplSyntaxOn\makeatletter
\RenewDocumentEnvironment { keywords } { O{ Keywords } }
   {
     \tex_global:D \tex_setbox:D \g_stm_key_box = \vtop \bgroup
     \hsize=.25 \textwidth
     %\cs_new:Nn \sep: { \par } % removed
     \def\sep{\par}             % \cs_set_eq:NN \sep \sep:
     \parindent \z@
     A,R,T,I,C,L,E\ \ I,N,F,O \par \skip_vertical:n { -3pt }
     \rule{.25 \textwidth}{.2pt}\par\footnotesize
     \noindent \textit { #1 }:  \par
   }
   { \egroup }
\ExplSyntaxOff\makeatother

Answer 2

Ok, here's a preliminary result of my analysis.

1st approach

Objective: make your files compile.

While doing so, my MikTeX console asked for a number of missing files to be installed, including the cas-dc.cls .

With the changes marked as % <<< !! I finally could make main.tex compile (with only the first subfile() call active). After changing sub1.tex as mentioned, both files compile separately, as they should.

Though there were warnings, the \sep error did not show up.

main.tex:

% 
%
\documentclass[a4paper,fleqn,twoside]{cas-dc}
\usepackage{subfiles}
\usepackage[numbers]{natbib}
\usepackage[T1,T2A]{fontenc}
\usepackage[utf8,]{inputenc}
%\usepackage{tempora}
%\usepackage{XCharter}
\usepackage{textcomp}
\usepackage[russian,ukrainian,romanian,english]{babel}
%\usepackage[dvipsnames,x11names]{xcolor}
\renewcommand{\rmdefault}{ftm}
\usepackage{yfonts}
\usepackage{multicol}
\usepackage{lineno,hyperref}
%\modulolinenumbers[5]
\usepackage{amsmath,amsfonts,amssymb,amsthm,mathtools,enumerate,float}
\sloppy
\makeatletter
\def\ps@first{%
\let@oddhead@empty
\let@evenhead@empty
\def@oddfoot{}
\let@evenfoot@oddfoot
}
\usepackage{wrapfig}
\usepackage{graphicx}
\renewcommand{\rmdefault}{cmr}
\renewcommand{\sfdefault}{cmss}
\renewcommand{\ttdefault}{cmtt}
%\renewcommand{\rmdefault}{cmss}
\renewcommand{\ttdefault}{cmss}
%\DeclareFontSubstitution{T2A}{cmr}{m}{n}
%\DeclareSymbolFont{T2Aletters}{T2A}{cmr}{m}{it}
\usepackage{geometry}
\renewcommand{\theenumi}{\arabic{enumi}}% Меняем везде перечисления на цифра.цифра
\renewcommand{\labelenumi}{\arabic{enumi}}% Меняем везде перечисления на цифра.цифра
\renewcommand{\theenumii}{.\arabic{enumii}}% Меняем везде перечисления на цифра.цифра
\renewcommand{\labelenumii}{\arabic{enumi}.\arabic{enumii}.}% Меняем везде перечисления на цифра.цифра
\renewcommand{\theenumiii}{.\arabic{enumiii}}% Меняем везде перечисления на цифра.цифра
\renewcommand{\labelenumiii}{\arabic{enumi}.\arabic{enumii}.\arabic{enumiii}.}% Меняем везде перечисления на цифра.цифра
\usepackage{fancyhdr}
\pagestyle{fancy}
\fancyhead{}
\fancyhead[LE,RO]{\thepage}
\fancyhead[CO]{ }
%\fancyhead[LO] {}
\fancyhead[CE]{ }
%\fancyhead[RE] { }
\renewcommand{\headrulewidth}{0.5pt}
\renewcommand{\footrulewidth}{0.5pt}
\fancyfoot[C]{}%}}  % <<< !!
{
\fancyfootoffset[R]{-12cm}
\fancyfoot[L]{}
\fancyfoot[C]{}
\fancyfoot[R]{}
\renewcommand{\footrulewidth}{0.3 mm}
\renewcommand{\headrulewidth}{0.3 mm}
}
\setlength{\voffset}{-10mm}
\setlength{\topmargin}{0mm}
\setlength{\headheight}{5mm}
\setlength{\headsep}{5mm}
\setlength{\footskip}{6mm}
%\newcommand{\l@abcd}[2]{\hbox to\textwidth{#1\dotfill #2}}
\usepackage{etoolbox}
\makeatletter
\patchcmd{\BR@backref}{\newblock}{\newblock(page~}{}{}
\patchcmd{\BR@backref}{\par}{)\par}{}{}
\makeatother
\usepackage[]{notes2bib}
\usepackage[nottoc]{tocbibind}
\usepackage[colorlinks]{hyperref}
%\hypersetup{pdffitwindow=true,linkcolor=LightSkyBlue,citecolor=Sienna,urlcolor=Navy,menucolor=black}
\hypersetup{
colorlinks=true,
linkcolor=magenta,
filecolor=blue,
urlcolor=blue,
citecolor=green,
anchorcolor=blue,
menucolor=blue,
backref=false,
backref=page,
pdfpagemode=UseNone,
pdfstartview=}
\RequirePackage[hyperpageref]{backref} 
\renewcommand{\backref}[1]{}

\renewcommand{\backrefalt}[4]{
\ifcase #1 
No cited.
\or
Cited on page #2.
\else
Cited on pages #2.
\fi}
\begin{document}
\subfile{sub1} % <<< !!
\subfile{sub2} % <<< !! (not used in 1st approach)
\end{document}

sub1.tex, wiht some parts missing (image) or obscure (\maketitle):

%\documentclass[document]{subfiles}
\documentclass[main]{subfiles} % <<< !!
\begin{document}
\title [mode = title]{ }
\tnotemark[1]
\tnotetext[1]{Research Paper}
\tnotetext[1]{This document is the result of blood, sweat, tears and taxpayer money.}
\nonumnote{This note has no numbers. In this work we demonstrate $a_b$
the formation Y_1 of a new type of polariton on the interface
between a cuprous oxide slab and a polystyrene micro-sphere placed
on the slab.}
\credit{Conceptualization of this study, Methodology, Software}
\author[2]{ }
[orcid=https://orcid.org/]
\cormark[2]
\fnmark[2]
\fntext[fn2]{ }
\ead{13335789@ukr.net}
\ead[URL]{www. }%
% Address/affiliation
\affiliation[2]{organization={National Scientific Center «Hon. Prof. M. S. Bokarius Forensic Science Institute»},
addressline={ },
city={ },
country={ }}
\credit{ }
\begin{abstract}
Abstract Text
\end{abstract}
\begin{keywords}
keywords
\vspace*{0.5\baselineskip}
\textbf{Article history:}\ Received: 30.09.2021\ Received in revised form: 19.12.2021 \Accepted: 9.01.2022 \Available online: 11.01.2022
\end{keywords}
%\maketitle % <<< !!
\section{ }
Text
\section{ }
text
\section{ } 
Text
\section{Conclusions} 
Text
\section{Conclusions}
Text 
\subsection{Acknowledgements}
Text
%\bio{{figs/image1}} % <<< !!
Author biography with author photo.
%\end{multicols} % <<< !!
\end{document}

2nd approach

How to provoke \sep errors ? Let's try including a second file:

• including sub1.tex did it (!)
• modifying sub1.tex into a slightly changed sub2.tex did it (!)

Note:

• with two different subfiles included in main

• sub1 went smoothly,

• while sub2 cause your error when compiling main.tex

  ! LaTeX Error: Control sequence \sep: already defined. For immediate help type H . ... l.44 \end {keywords}

So, where is it?

I proved by:

• commenting out the whole keyword environment (no error)
• allowing only the \begin \end statements (error)

it's here:

% <<< !!!
\begin{keywords}
%keywords
%\vspace*{0.5\baselineskip}
%\textbf{Article history:}\\ Received: 30.09.2021\\ Received in revised form: 19.12.2021 \\Accepted: 9.01.2022 \\Available online: 11.01.2022
\end{keywords}

You probably need to \renewenvironment the keyword environment, or a similar action.

Conclusion

In this case a stepwise enhancement of code was sufficient to cause the error. Reading the error message made it simple to localize the trouble maker: an environment.

Maybe somebody who knows the cas-dc.cls class by heart has a cure for you.

However, some work is left to do, like adjusting the counters, as the main.pdf generated without the trouble maker shows: