Nested macros and hyperlink problem

Question

I am new to LaTeX and write a document with the use of the hyperref package. Here is this simple scenario which I do not understand. I have to use a macro like \ccc in \hyperlink but it causes 6 errors and I can not fix the problem:

\documentclass[a4paper,12pt,oneside]{book}
\usepackage{hyperref}
\begin{document}
\hypertarget{link:two}{targettwo}

\newcommand{\aaa}{link:one}
\newcommand{\ccc}{\renewcommand{\aaa}{link:two} \aaa}
\hyperlink{\ccc}{something} %no link produced, only text: "link:two" and 6 errors
\end{document}

log:
.
.
.
! Use of \hyper@link@ doesn't match its definition.
\@ifnextchar ... \reserved@d =#1\def \reserved@a {
                                                  #2}\def \reserved@b {#3}\f...
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
If you say, e.g., `\def\a1{...}', then you must always
put `1' after `\a', since control sequence names are
made up of letters only. The macro here has not been
followed by the required stuff, so I'm ignoring it.

! Argument of \@firstoftwo has an extra }.
<inserted text> 
                \par 
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
I've run across a `}' that doesn't seem to match anything.
For example, `\def\a#1{...}' and `\a}' would produce
this error. If you simply proceed now, the `\par' that
I've just inserted will cause me to report a runaway
argument that might be the root of the problem. But if
your `}' was spurious, just type `2' and it will go away.

Runaway argument?
! Paragraph ended before \@firstoftwo was complete.
<to be read again> 
                   \par 
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.

! Extra }, or forgotten \endgroup.
\hyper@link@ ...\Hy@safe@activestrue \edef \x {#3}
                                                  \ifx \Hy@tempa \@empty \to...
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
I've deleted a group-closing symbol because it seems to be
spurious, as in `$x}$'. But perhaps the } is legitimate and
you forgot something else, as in `\hbox{$x}'. In such cases
the way to recover is to insert both the forgotten and the
deleted material, e.g., by typing `I$}'.

Runaway argument?
{\let \reserved@d =*\def 
! Paragraph ended before \hyper@link was complete.
<to be read again> 
                   \par 
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
I suspect you've forgotten a `}', causing me to apply this
control sequence to too much text. How can we recover?
My plan is to forget the whole thing and hope for the best.

! Too many }'s.
\x ...r@link {link}{\let \reserved@d =*\def \par }
                                                  {\Hy@safe@activesfalse aaa}
l.21 \hyperlink{\ccc}{aaa}
                           %6 errors
You've closed more groups than you opened.
Such booboos are generally harmless, so keep going.
.
.
.

I am Using TeXnicCenter with MikTeX 2.9.

Welcome to TeX.SX! What's the purpose of this nesting? There may be better ways to do this. — egreg, Apr 11 '12 at 07:46

Martin Scharrer · Accepted Answer · 2012-04-13T13:00:09.233

4

The correct syntax is \hyperlink{<name>}{<text>} where <name> must be a valid, expandable label name. It can not contain any non-expandable commands. This excludes any form of assignment, e.g. \renewcommand. The name must instead expand directly to some text only.

So your:

\newcommand{\aaa}{link:one}
\newcommand{\ccc}{\renewcommand{\aaa}{link:two} \aaa}
\hyperlink{\ccc}{something}

is wrong and will never work. You need to write it some way like this:

\newcommand{\aaa}{link:one}
\newcommand{\ccc}{\renewcommand{\aaa}{link:two}}
\ccc
\hyperlink{\aaa}{something}

This means: Do any redefinition of \aaa before \hyperlink and make sure that \aaa expands to only the name.

If you give a more specific example of your exact use, then we can help you further.

edited Apr 13 '12 at 13:00

answered Apr 13 '12 at 12:56

Martin Scharrer

262,582

I can't understand why your example (now) and my work. – Marco Daniel Apr 13 '12 at 13:09
@MarcoDaniel: The now gone "example" was the original text posted in the question. I only accidentally pasted it at the end of my answer. ;-) Note that a simple expandable macro works, because it is expanded internally. Either using \csname .. \endcsname or by writing it into an auxiliary file. Both do not support unexpandable stuff. – Martin Scharrer Apr 13 '12 at 13:10
Should I remove my answer? – Marco Daniel Apr 13 '12 at 13:27
@MarcoDaniel: If you think so. Using $ccc doesn't make much sense IMO. – Martin Scharrer Apr 13 '12 at 13:35
@MartinScharrer: Problem is solved I gess, thanks. But in every real case one should be able to get the macro's output in a fully expandable form. Is there any common way to do this?(same question in: http://tex.stackexchange.com/questions/51770/why-hyperlink-rightmark-does-not-work-in-fancyhead-and-inside-some-other-m ) – pmks Apr 13 '12 at 14:24

Nested macros and hyperlink problem

1 Answers1

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