Chemical numbering

Question

The XyMTeX package defines the environment XyMcompd{name} that results in a counter \cref{name} pointing to the compound "name". I would like to know what are the basic steps for this macro \cref and how complex it will be to rebuild it without the package XyMTeX.

Thanks for your help

Bernhard

Answer 1

You can find the complete compound labeling mechanism of XyMTeX in the file chemist.sty:

\@ifundefined{chapter}{\newcounter{compd}}{\newcounter{compd}[chapter]}
\def\thecompd{\arabic{compd}}
\def\compd{\leavevmode\refstepcounter{compd}{\large\bf \thecompd}}
\def\nocompd{\refstepcounter{compd}}
\def\compdlabel#1{\compd \label{#1}}
\def\nocompdlabel#1{\nocompd \label{#1}}
\@ifundefined{bf}{\def\bf{\normalfont\bfseries}}{}
\def\cref#1{{\bf \ref{#1}}}

---

Let's go through it:

\@ifundefined{chapter}{\newcounter{compd}}{\newcounter{compd}[chapter]}

This defines a counter compd which if a macro \chapter exists is added to the counter chapter's reset list.

\def\thecompd{\arabic{compd}}

This redefines \thecompd from \@arabic \c@compd to \arabic{compd} which is basically redundant.

\def\compd{\leavevmode\refstepcounter{compd}{\large\bf \thecompd}}

This defines a macro \compd which steps said counter and prints the number in bold and large. The environment XyMcompd which you mention in your question uses this macro if the corresponding argument is not empty.

\def\nocompd{\refstepcounter{compd}}

This defines a macro \nocompd which steps said counter but doesn't print the number.

\def\compdlabel#1{\compd \label{#1}}

This defines a macro \compdlabel with a mandatory argument which steps the counter, prints the number and adds a label using the argument.

\def\nocompdlabel#1{\nocompd \label{#1}}

The same but doesn't print the number.

\@ifundefined{bf}{\def\bf{\normalfont\bfseries}}{}

This checks if \bf is undefined and if it is defines it to be \normalfont\bfseries.

\def\cref#1{{\bf \ref{#1}}}

This defines \cref to take an argument to refer to a label and prints it in bold.

---

Here is some slightly modified code which copies this:

\documentclass{article}

\newcounter{compound}
\newcommand*\compoundformat[1]{\textbf{\large#1}}
\newcommand*\compound{\leavevmode\refstepcounter{compound}\compoundformat{\thecompound}}
\newcommand*\nocompound{\refstepcounter{compound}}
\newcommand*\compoundlabel[1]{\compound\label{#1}}
\newcommand*\nocompoundlabel[1]{\nocompound\label{#1}}
\newcommand*\compoundref[1]{\compoundformat{\ref{#1}}}

\begin{document}

foo \compound\ bar and \compoundlabel{ethanol} and later \compoundref{ethanol}.

\end{document}

As comparison the corresponding code with XyMTeX:

\documentclass{article}
\usepackage{xymtex}

\begin{document}

foo \compd\ bar and \compdlabel{ethanol} and later \cref{ethanol}.

\end{document}

Answer 2

I used the code from XyMTeX, and the structures are labeled, however the references are still missing which I do not understand since they are inside a float which should give the proper reference at least for the \mevalonate macro.

@Clemens BTW Using your code and the \compoundlabel and \compoundref pair resulted in the same warnings: Latex failed to resolve 2 reference(s)

\documentclass[12pt,a4paper]{book}
\usepackage[ngerman]{babel}
\usepackage[utf8]{inputenc}
\usepackage{graphicx,float,hyperref,calc,caption,mwe}
\newfloat{Mycomp}{hbtp}{cmp}[chapter] % programmed figures
\floatname{Mycomp}{}
\makeatletter\let\ftype@Mycomp\ftype@figure % figure and compound are 
\setlength{\unitlength}{0.1mm}
%taken from chemist.sty from the XyMTex package
\@ifundefined{chapter}{\newcounter{compd}}{\newcounter{compd}[chapter]}
\def\thecompd{\arabic{compd}}
\def\compd{\leavevmode\refstepcounter{compd}{\large\bf \thecompd}}
\def\nocompd{\refstepcounter{compd}}
\def\compdlabel#1{\compd \label{#1}}
\def\nocompdlabel#1{\nocompd \label{#1}}
\@ifundefined{bf}{\def\bf{\normalfont\bfseries}}{}
\def\cref#1{{\bf \ref{#1}}}

\DeclareRobustCommand{\mevalonate}{%
%
\begin{Mycomp}[H]
\fbox{
    \parbox[c]{450\unitlength}{%
    \centering  
    {\large\bfseries Mevalonate}\quad\compdlabel{Mevalonat}\\\vspace*{.5em}

    \includegraphics[width=400\unitlength]{example-image-a}
    }%
}
\end{Mycomp}
}
\DeclareRobustCommand{\mevalonatePP}{%
%
\fbox{
    \parbox[c]{450\unitlength}{%
    \centering  
    {\large\bfseries Mevalonate pyrophosphate}\quad\compdlabel{MevalonatPP}\\\vspace*{.5em}

    \includegraphics[width=400\unitlength]{example-image-b}
}%
}
}
\begin{document}

\mevalonate     \mevalonatePP

In the text you will refer to the structures by \cref{mevalonatePP} and \cref{mevalonate}.

\end{document}