General ⇒ use definition as an argument to another command

[Anymouse]

Suppose I have something like

Code: Select all

\newcommand{\isbn}{978-1-56619-909-4}

Then later in the document (e.g. the back page) I want to do

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\EANisbn[ISBN=\isbn{},SC5b]

That doesn't work.

How is that kind of thing accomplished? I know with EANisbn command you can just specify the ISBN when you first \usepackage[]{} but in general, how does one pass a variable option to a macro?

[Ijon Tichy]

Usually it does work:

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\documentclass{article}
\usepackage{keyval}
\newcommand{\isbn}{978-1-56619-909-4}
\makeatletter
\define@key{EAN}{ISBN}{Current ISBN is #1. }
\define@key{EAN}{SC5b}[true]{Option SC5b is #1. }
\makeatother
\newcommand\EANisbn[1][]{%
  \setkeys{EAN}{#1}%
}
\begin{document}
\EANisbn[ISBN=\isbn{},SC5b]
\end{document}

or somehow more realistic:

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\documentclass{article}
\usepackage{keyval}
\newcommand{\isbn}{978-1-56619-909-4}
\makeatletter
\newcommand*{\EANISBN}{}
\newif\ifEANSCvb
\define@key{EAN}{ISBN}{\edef\EANISBN{#1}}
\define@key{EAN}{SC5b}[true]{\expandafter\let\expandafter\ifEANSCvb\csname if#1\endcsname}
\makeatother
\newcommand\EANisbn[1][]{%
  \setkeys{EAN}{#1}%
}
\begin{document}
\EANisbn[ISBN=\isbn,SC5b]
Current ISBN is \EANISBN{} and SC5b is \ifEANSCvb true\else false\fi.
\end{document}

or

Code: Select all

\documentclass{article}
\usepackage{keyval}
\newcommand{\isbn}{978-1-56619-909-4}
\makeatletter
\newcommand{\EANISBN}{}
\newif\ifEANSCvb
\define@key{EAN}{ISBN}{\expandafter\renewcommand\expandafter\EANISBN\expandafter{#1}}
\define@key{EAN}{SC5b}[true]{\expandafter\let\expandafter\ifEANSCvb\csname if#1\endcsname}
\makeatother
\newcommand\EANisbn[1][]{%
  \setkeys{EAN}{#1}%
}
\begin{document}
\EANisbn[ISBN=\isbn,SC5b]
Current ISBN is \EANISBN{} and SC5b is \ifEANSCvb true\else false\fi.
\end{document}

So please show us a minimal working example that makes your problem reproducible.

[Anymouse]

Thank you!
I will have time to try these probably tomorrow.

[Anymouse]

Okay test case to show what should result:

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\documentclass{article}
\newcommand{\isbn}{978-1-56619-909-4}
\usepackage{ean13isbn}
\begin{document}
\EANisbn[ISBN=978-1-56619-909-4,SC5b]
\end{document}

Test case to show error when using definition within another:

Code: Select all

\documentclass{article}
\newcommand{\isbn}{978-1-56619-909-4}
\usepackage{ean13isbn}
\begin{document}
\EANisbn[ISBN=\isbn{},SC5b]
\end{document}

It results in "! Missing = inserted for \ifnum" error

[Ijon Tichy]

The used package does not expand the value before testing whether it is a number. So you have to do the expansion yourself, e.g.

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\documentclass{article}
\newcommand{\isbn}{978-1-56619-909-4}
\newcommand{\ISBNoption}{}
\edef\ISBNoption{ISBN=\isbn}
\usepackage{ean13isbn}
\begin{document}
\expandafter\EANisbn\expandafter[\ISBNoption,SC5b]
\end{document}

or use another package like

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\documentclass{article}
%\usepackage[undo-recent-deprecations]{expl3}% Only needed with out-dated GS1 and up-to-date expl3
\newcommand{\isbn}{978-1-56619-909-4}
\usepackage{GS1}[2021/06/17]% Need at least GS1 version 23 (see note below).
\begin{document}
\GSSetup{module_width=.46mm}
\expandafter\EANBarcode\expandafter{\isbn}
\end{document}

Note: GS1 before version 23 is not compatible with current version of l3kernel. If you get an error about the usage of deprecated \hbox_unpack_clear, you have to activate loading expl3 with option undo-recent-deprecations or—better!—update to GS1 version 23 or newer

[Anymouse]

Thank you! That worked