custom counter and cross-referencing

Question

I created a custom counter 'rtaskno' and a command '\rtask' as following:

\newcounter{rtaskno}
\newcommand{\rtask}{%
   \stepcounter{rtaskno}%
   \thertaskno}

I like to use them as following:

\section{Task \rtask. Blah Blah..}

\section{Task \rtask. Blah Blah..}

\section{Task \rtask. Blah Blah..}

\section{Task \rtask. Blah Blah..}

Later in the text, if I want to cross-reference 'Task 3', how can I do it? Where to put label?

Answer 1

There are tricky timing issues in your problem. If you are going to prepare a table of contents the thing as it is now will bomb out.

Probably the best thing to do is to use a two-pass strategy:

\newcounter{rtaskno}
\newcommand{\rtask}[1]{\refstepcounter{rtaskno}\label{#1}}

When you want to use the task number in your section titles you'll write

\rtask{label}
\section{Task \ref{label}. Blah}

Answer 2

You will need to use \refstepcounter rather than \stepcounter to make your counter "visible" to the referencing mechanism. The label can go anywhere after the \refstepcounter as long as it's before the next \refstepcounter (for example the next theorem environment, section heading etc...

Using it inside a section heading might be tricky.

Answer 3

There are two things that deserve attention: 1) you need to use \refstepcounter instead of \stepcounter, and 2) since you are going to use \rtask inside a sectionning command you will have to protect it, or even better, declare it as robust from the beginning. I also included an argument of the definition, so that you can have the necessary label for cross-references:

EDIT: this approach will fail miserably if a table of contents is created. A possible workaround would be to use the optional argument for \section, but I don't like this option so much. For a proper possible solution when a ToC is created, see egreg's answer.

\documentclass{article}

\newcounter{rtaskno}
\DeclareRobustCommand{\rtask}[1]{%
   \refstepcounter{rtaskno}%
   \thertaskno\label{#1}}

\begin{document}

\section{Task \rtask{task:one}. Blah Blah..}

\section{Task \rtask{task:two}. Blah Blah..}

\section{Task \rtask{task:three}. Blah Blah..}

\section{Task \rtask{task:four}. Blah Blah..}

Task~\ref{task:four}

\end{document}

Answer 4

you could create a new command for this:

\newcommand{\newTask}[2]{\section{Task \rtask. #2}\label{#1}}

and use it as such:

\newTask{t:first}{Blah Blah..}
\newTask{t:second}{Blah Blah..}
\newTask{t:third}{Blah Blah..}