cleveref not supporting a language

Question

I want a document where you can select between two languages and use cleveref. However, cleveref does not support the second language nynorsk. I still want to be able to use the english version, so I can not simply use \crefname to redefine the names. Here is an example (note that cref is provided in english):

\documentclass[5p,a4paper]{elsarticle}

\usepackage[english,nynorsk]{babel}
\usepackage{hyperref}
\usepackage[english,nynorsk]{cleveref}
\usepackage{appendix}

\begin{document}
\selectlanguage{nynorsk} % Switch between english and nynorsk

\begin{equation}
    E=mc^2 \label{eq:E=mc}
\end{equation}

\Cref{eq:E=mc}

\appendix

\section{A} % To check that current language option is working.

\end{document}

My question is: How can I define the cref names for the language nynorsk whilst still being able to use the english versions?

I was thinking of maybe using if statements to check if the selected language is nynorskand if it is, use the appropriate names. I also am considering to send an email to the maintainer of the cleveref package with the appropriate code for the .sty file to include this language (as a long term solution).

Answer 1

You have to do almost no language checking yourself, if you use cleveref's interface to define language-specific definitions. This interface is internal and not documented, so things could theoretically break in future versions, so I only recommend this for testing and the short term. A medium- to long-term solution would be to contact the maintainer and ask him to include language support for nynorsk directly in the package.

For the example I just copied the language definitions from norsk to nynorsk, so you will have to translate the terms yourself.

\documentclass[5p,a4paper,nynorsk,english]{elsarticle}

\usepackage{babel}
\usepackage{hyperref}
\usepackage{cleveref}
\usepackage{appendix}

\makeatletter
\cref@addlanguagedefs{nynorsk}{%
  \PackageInfo{cleveref}{loaded `nynorsk' language definitions}%
  \renewcommand{\crefrangeconjunction}{ til\nobreakspace}%
  \renewcommand\crefrangepreconjunction{}%
  \renewcommand\crefrangepostconjunction{}%
  \renewcommand{\crefpairconjunction}{ og\nobreakspace}%
  \renewcommand{\crefmiddleconjunction}{, }%
  \renewcommand{\creflastconjunction}{ og\nobreakspace}%
  \renewcommand{\crefpairgroupconjunction}{ og\nobreakspace}%
  \renewcommand{\crefmiddlegroupconjunction}{, }%
  \renewcommand{\creflastgroupconjunction}{ og\nobreakspace}%
 %
  \Crefname{equation}{Likning}{Likningene}%
  \Crefname{figure}{Figur}{Figurene}%
  \Crefname{subfigure}{Figur}{Figurene}%
  \Crefname{table}{Tabell}{Tabellene}%
  \Crefname{subtable}{Tabell}{Tabellene}%
  \Crefname{page}{Side}{Siden}%
  \Crefname{part}{Del}{Delene}%
  \Crefname{chapter}{Kapittel}{Kapitlene}%
  \Crefname{section}{Avsnitt}{Avsnittene}%
  \Crefname{subsection}{Avsnitt}{Avsnittene}%
  \Crefname{subsubsection}{Avsnitt}{Avsnittene}%
  \Crefname{appendix}{Tillegg}{Tilleggene}%
  \Crefname{subappendix}{Tillegg}{Tilleggene}%
  \Crefname{subsubappendix}{Tillegg}{Tilleggene}%
  \Crefname{subsubsubappendix}{Tillegg}{Tilleggene}%
  \Crefname{enumi}{Punkt}{Punktene}%
  \Crefname{enumii}{Punkt}{Punktene}%
  \Crefname{enumiii}{Punkt}{Punktene}%
  \Crefname{enumiv}{Punkt}{Punktene}%
  \Crefname{enumv}{Punkt}{Punktene}%
  \Crefname{footnote}{Fotnote}{Fotnotene}%
  \Crefname{theorem}{Teorem}{Teoremene}%
  \Crefname{lemma}{Lemma}{Lemma}%
  \Crefname{corollary}{Korollar}{Korollarene}%
  \Crefname{proposition}{P\aa stand}{P\aa standene}%
  \Crefname{definition}{Definisjon}{Definisjonene}%
  \Crefname{result}{Resultat}{Resultatene}%
  \Crefname{example}{Eksempel}{Eksemplene}%
  \Crefname{remark}{Bemerkning}{Bemerkningene}%
  \Crefname{note}{Note}{Notene}%
  \Crefname{algorithm}{Algoritme}{Algoritmene}%
  \Crefname{listing}{Opplisting}{Opplistingene}%
  \Crefname{line}{Linje}{Linjene}%
 %
  \if@cref@capitalise%
    \crefname{equation}{Likning}{Likningene}%
    \crefname{figure}{Figur}{Figurene}%
    \crefname{subfigure}{Figur}{Figurene}%
    \crefname{table}{Tabell}{Tabellene}%
    \crefname{subtable}{Tabell}{Tabellene}%
    \crefname{page}{Side}{Siden}%
    \crefname{part}{Del}{Delene}%
    \crefname{chapter}{Kapittel}{Kapitlene}%
    \crefname{section}{Avsnitt}{Avsnittene}%
    \crefname{subsection}{Avsnitt}{Avsnittene}%
    \crefname{subsubsection}{Avsnitt}{Avsnittene}%
    \crefname{appendix}{Tillegg}{Tilleggene}%
    \crefname{subappendix}{Tillegg}{Tilleggene}%
    \crefname{subsubappendix}{Tillegg}{Tilleggene}%
    \crefname{subsubsubappendix}{Tillegg}{Tilleggene}%
    \crefname{enumi}{Punkt}{Punktene}%
    \crefname{enumii}{Punkt}{Punktene}%
    \crefname{enumiii}{Punkt}{Punktene}%
    \crefname{enumiv}{Punkt}{Punktene}%
    \crefname{enumv}{Punkt}{Punktene}%
    \crefname{footnote}{Fotnote}{Fotnotene}%
    \crefname{theorem}{Teorem}{Teoremene}%
    \crefname{lemma}{Lemma}{Lemma}%
    \crefname{corollary}{Korollar}{Korollarene}%
    \crefname{proposition}{P\aa stand}{P\aa standene}%
    \crefname{definition}{Definisjon}{Definisjonene}%
    \crefname{result}{Resultat}{Resultatene}%
    \crefname{example}{Eksempel}{Eksemplene}%
    \crefname{remark}{Bemerkning}{Bemerkningene}%
    \crefname{note}{Note}{Notene}%
    \crefname{algorithm}{Algoritme}{Algoritmene}%
    \crefname{listing}{Opplisting}{Opplistingene}%
    \crefname{line}{Linje}{Linjene}%
 %
  \else%
    \crefname{equation}{likning}{likningene}%
    \crefname{figure}{figur}{figurene}%
    \crefname{subfigure}{figur}{figurene}%
    \crefname{table}{tabell}{tabellene}%
    \crefname{subtable}{tabell}{tabellene}%
    \crefname{page}{side}{siden}%
    \crefname{part}{del}{delene}%
    \crefname{chapter}{kapittel}{kapitlene}%
    \crefname{section}{avsnitt}{avsnittene}%
    \crefname{subsection}{avsnitt}{avsnittene}%
    \crefname{subsubsection}{avsnitt}{avsnittene}%
    \crefname{appendix}{tillegg}{tilleggene}%
    \crefname{subappendix}{tillegg}{tilleggene}%
    \crefname{subsubappendix}{tillegg}{tilleggene}%
    \crefname{subsubsubappendix}{tillegg}{tilleggene}%
    \crefname{enumi}{punkt}{punktene}%
    \crefname{enumii}{punkt}{punktene}%
    \crefname{enumiii}{punkt}{punktene}%
    \crefname{enumiv}{punkt}{punktene}%
    \crefname{enumv}{punkt}{punktene}%
    \crefname{footnote}{fotnote}{fotnotene}%
    \crefname{theorem}{teorem}{teoremene}%
    \crefname{lemma}{lemma}{lemma}%
    \crefname{corollary}{korollar}{korollarene}%
    \crefname{proposition}{p\aa stand}{p\aa standene}%
    \crefname{definition}{definisjon}{definisjonene}%
    \crefname{result}{resultat}{resultatene}%
    \crefname{example}{eksempel}{eksemplene}%
    \crefname{remark}{bemerkning}{bemerkningene}%
    \crefname{note}{note}{notene}%
    \crefname{algorithm}{algoritme}{algoritmene}%
    \crefname{listing}{opplisting}{opplistingene}%
    \crefname{line}{linje}{linjene}%
  \fi}% end \cref@loadlanguagedefs
\makeatother

\begin{document}
\Cref{eq:E=mc}

\selectlanguage{nynorsk} % Switch between english and nynorsk

\begin{equation}
  E=mc^2 \label{eq:E=mc}
\end{equation}

\Cref{eq:E=mc}

\appendix

\section{A} % To check that current language option is working.


\end{document}

There is one caveat. Due to the implementation of the language options our new language will not work correctly if it is the document main language. In that case it helps to explicitly switch the language to the main language directly after \begin{document}. This is just a small hitch that won't be relevant once cleveref supports your language out of the box, though.