Emphasize the first reference to a figure or table

Question

I'm writing a scientific report and it's required that the first reference to any figure or table (not to equations or sections) in the text is set bold like this:

Is there a package for this kind of task?

The acronym package does something similar giving the full description of an acronym when it's used for the first time, so I guess it's not a too special problem.

Answer 1

The following works:

\documentclass{article}
\makeatletter
\def\@setref#1#2#3{%
  \ifx#1\relax
    \protect\G@refundefinedtrue
    \nfss@text{\reset@font\bfseries ??}%
    \@latex@warning{Reference `#3' on page \thepage \space
      undefined}%
  \else
    \expandafter\ifx\csname used@#1\endcsname\relax
      \expandafter\global\expandafter\def\csname used@#1\endcsname{used}%
      {\bfseries\expandafter#2#1\null}% Formatting of first reference
    \else
      \expandafter#2#1\null%
    \fi
  \fi%
}
\makeatother
\begin{document}
\begin{figure}
  \centering\rule{150pt}{20pt}
  \caption{A figure}\label{fig:figure}
\end{figure}
See Figure~\ref{fig:figure}. The same reference to Figure~\ref{fig:figure}.
\end{document}

It modifies the macro \@setref which is called from \ref to decide whether a reference exists or not. The formatting is based on a condition to check whether a newly defined macro used@<label> exists or not.

Formatting of the first reference is set using \bfseries and can be modified to suit.