Reproducibly generating unique numbers

Question

I'm doing a software specification in LaTeX and it is considered best practice to assign a unique number to each requirement. Chapter numbers are not an option for this, because those numbers have to stay the same even if I new requirements are added in the middle of the existing ones.

The only option I see so far is to assign those numbers manually. But this does not guaranty uniqueness and becomes messy at the point multiple persons are involved.

Do you have any suggestions?

Answer 1

Better Solution:

I would recommend that each requirement be manually labelled, and ensure that duplicates are not used. The MWE below produces:

but if you had accidentally used the same environment label (ie, if the last one was used as \begin{Requirement}{1}, this produces:

Package Requirement Error: Duplicate Requirement: 1.

so the author would be made aware that a different requirement label needed to be used.

This version is based on Ulrike Fischer's suggestion:

Code:

\documentclass{article}
\usepackage{xstring}
\newcommand\CheckForDuplicateRequirement[1]{%
    \ifcsname Requirement#1\endcsname %
        \PackageError{Requirement}{Duplicate Requirement: #1}{}%
    \else%
        \expandafter\gdef\csname Requirement#1\endcsname{}%
    \fi%
}
\newenvironment{Requirement}[1]{%
    \CheckForDuplicateRequirement{#1}%
    \textbf{Requirement #1:}%
}{%
}%
\begin{document}
\begin{Requirement}{1}
  This is the first requirement
\end{Requirement}
\begin{Requirement}{X}
  This is the second requirement
\end{Requirement}
\begin{Requirement}{Z}
  This is the third requirement
\end{Requirement}
\end{document}

---

Old Solution:

This solution builds a list of the references using How keep a running list of strings and then process them one at a time, and issues a \PackageError if a duplicate requirement label is provided

Notes:

• With this approach, the labels can be numbers and/or letters but should not contain <, or > as I use that as a delimiter for the strings. This is to ensure that test works properly for labels that are sub-strings of other labels. Previous version would have reported a duplicate if the label was XX was used followed by X.

Code:

\documentclass{article}
\usepackage{xstring}
\newcommand\RequirementList{}
\newcommand\CheckForDuplicateRequirement[1]{%
\StrPosition{\RequirementList}{<#1>}[\Position]
    \IfEq{\Position}{0}{%
        \global\edef\RequirementList{\RequirementList<#1>}%
    }{%
        \PackageError{Requirement}{Duplicate Requirement: #1}{}%
    }%
}
\newenvironment{Requirement}[1]{%
    \CheckForDuplicateRequirement{#1}%
    \textbf{Requirement #1:}%
}{%
}%
\begin{document}
\begin{Requirement}{1}
  This is the first requirement
\end{Requirement}
\begin{Requirement}{X}
  This is the second requirement
\end{Requirement}
\begin{Requirement}{Z}
  This is the third requirement
\end{Requirement}
\end{document}