How to make a custom reference list without automatic counter

Question

In my document I have a list of requirements (currently these are just text created through a custom command).

One special thing is that these requirements are manually numbered (and not ordered by number). This is very important because that way we can assure requirements stay uniquely identifiable across documents and versions.

How can I make a list of requirements? And how can I refer (clickable in PDF) to my requirements from the text?

I have found several examples of this (for instance using ntheorem), but they all do the numbering automatically.

This could work for example as follows (the requirements are spread across the document):

\requirement{7}{Important requirement}
...
\requirement{8}{Secondary requirement}
...
\requirement{3}{Moved requirement, this must be followed if \refRequirement{7} is not follow}

\listOfRequirements

This would produce the requirements in order of set in the document, with a clickable link to requirement 7, and alist of requirements (sorted by number) in a separate chapter, these indicate the page the requirement is on, as well as a link to them.

Answer 1

Here's a solution that does both of your requests; let's go through the code.

The line

\newcommand\listOfRequirements{\@starttoc{req}}

starts a file called \jobname.req to which we will write the requirements. The \requirement command is defined as

\newcommand{\requirement}[2]{%
    \hypertarget{req:#1}
    #1. #2%
    \phantomsection
    \addcontentsline{req}{subsection}{\protect\numberline{\protect#1} #2}%
}

which

• sets a hypertarget to be used by the \refRequirement command (more on that in a moment)
• outputs #1 and #2 to the document
• sets a phantomsection which is necessary for the hyperlinks to work
• adds a numbered entry containing #2 with #1 as its number to \jobname.rec

Finally, the \refRequirement command hyperlinks to the original location of the requirement.

\newcommand{\refRequirement}[1]{\hyperlink{req:#1}{#1}}

As with any toc-based command, it takes at least two compilations to stabilize (possibly more if you have any other changing toc type elements).

% arara: pdflatex
% arara: pdflatex
% !arara: indent: {overwrite: on}
\documentclass{report}
\usepackage{lipsum}
\usepackage{hyperref}

\makeatletter
% requirements
\newcommand\listOfRequirements{\@starttoc{req}}
% command to output requirement on the page, and also add it
% to the list of requirements
\newcommand{\requirement}[2]{%
    \hypertarget{req:#1}
    #1. #2%
    \phantomsection
    \addcontentsline{req}{subsection}{\protect\numberline{\protect#1} #2}%
}

\newcommand{\refRequirement}[1]{\hyperlink{req:#1}{#1}}

\begin{document}

\begin{itemize}
    \item here's a reference to requirement \refRequirement{7}
    \item here's a reference to requirement \refRequirement{3}
    \item here's a reference to requirement \refRequirement{8}
\end{itemize}
\lipsum

\requirement{7}{Important requirement}

\lipsum

\requirement{8}{Secondary requirement}

\lipsum

\requirement{3}{Moved requirement, this must be followed if  is not follow}

\lipsum


\chapter{Requirements}
\listOfRequirements
\end{document}

Answer 2

To get the numbering and the reference you only need to set the number at the begin of your command to Arg-1 and then use \refstepcounter:

\documentclass{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}%
\usepackage{hyperref}
\newcounter{requirement}
\newcommand\requirement[1]{%
 \par
 \setcounter{requirement}{\the\numexpr #1-1}% number -1
 \refstepcounter{requirement}% +1 
 \therequirement:}
\begin{document}
\requirement{3} blablablaq\label{a}

\requirement{7} blablablaq\label{b}


\newpage

see requirement \ref{b}

\end{document}