<html><head><meta name="color-scheme" content="light dark"></head><body><pre style="word-wrap: break-word; white-space: pre-wrap;">\documentclass[a4paper,12pt]{report}
\makeatletter
\newcommand{\textarrow}[2][1]
  { \settowidth{\@tempdima}{#2}
    \stackrel{#2}
             {\makebox[#1\@tempdima][l]{\rightarrowfill}}
  }
\makeatother

\begin{document}


\begin{eqnarray*}
 y = f(x) &amp; \textarrow[1.5]{Transformation} &amp; Y = F(X)\\
 y = f(x) &amp; \textarrow{\ensuremath{x\mapsto X}} &amp; Y = F(X)
\end{eqnarray*}

\end{document}
</pre></body></html>