Highlighting text and equations

[jfh]

I have just received a MS back with referees' comments. The journal
editor wants changes highlighted. These include text, math mode in-
line, displayed equations, and figures. I tried the following:

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{color,soul}
\begin{document}
blah \hl{blah} blah \hl{$x=x$}
\hl{
\begin{gather}
x=y
\end{gather}
}
\end{document}

If I remove \hl{ before \begin{gather} and } after \end{gather} I get
yellow highlighting for both the plain text blah and the in-line
equation $x=x$ but if I don't, the error message is

! LaTeX Error: Environment {gather} undefined.
See the LaTeX manual or LaTeX Companion for explanation.
Type H <return> for immediate help.
...
l.10 }

What should I do instead?

-- John Harper

[Gonzalo Medina Arellano]

You could use the shaded environment from the framed package (http://
www.ctan.org/pkg/framed):

\documentclass{article}
\usepackage{amsmath,amssymb}
\usepackage{xcolor,soul,framed,caption}

\colorlet{shadecolor}{yellow}

\begin{document}
blah \hl{blah} blah \hl{$x=x$}

\begin{shaded}

\begin{gather}
x=y
\end{gather}

\end{shaded}

\begin{shaded}
\centering
\rule{4cm}{2cm} % just to simulate an actual figure
\captionof{figure}{Test figure}
\end{shaded}

\end{document}

you cannot use floats inside shaded, but you could use the \captionof
command from the caption package, as the example shows.