# Are nath and xcolor incompatible?

I have a file that compiles fine. It uses nath and color packages:

\documentclass[10pt,a4paper]{article}
\usepackage{color}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow (B)$$
\end{document}


But as soon as I try to color (B), I get an error extra {. The complete file (which does not compile) is:

\documentclass[10pt,a4paper]{article}
\usepackage{color}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow {\color{red}(B)}$$
\end{document}


Removing the nath package and \delimgrowth command fixes the error. The following code compiles fine.

\documentclass[10pt,a4paper]{article}
\usepackage{color}

\begin{document}
$$A \Rightarrow {\color{red}(B)}$$
\end{document}


Also, If I remove the braces around B, the error is gone. The following code compiles fine:

\documentclass[10pt,a4paper]{article}
\usepackage{color}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow {\color{red}B}$$
\end{document}


Thanks to @egreg for pointing out that nath does not like paretheses hidden away inside braces. The following code also does not compile:

\documentclass[10pt,a4paper]{article}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow {(B)}$$
\end{document}


So, my question is: Is there a way to have colored equations in a file that uses nath to automatically resize nested parentheses?

I learned about the nath package from automatic size adjustment for nested parentheses.

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Please make a complete small document that shows all the packages loaded so the problem may be reproduced. –  David Carlisle Nov 27 '12 at 23:04
@DavidCarlisle Did that. Thanks –  Abhishek Nov 27 '12 at 23:12
Try \textcolor{red}{(B)} instead of {\color{red}(B)} –  egreg Nov 27 '12 at 23:15
@egreg That does not fix the error. Thanks anyways –  Abhishek Nov 27 '12 at 23:16
You get the same error with A \Rightarrow {(B)} and without loading color. So this is a problem of nath that doesn't like parentheses hidden by braces. –  egreg Nov 27 '12 at 23:19

You get the same error with the following document:

\documentclass[10pt,a4paper]{article}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow {(B)}$$
\end{document}


with or without \delimgrowth, because nath doesn't like the parentheses to be hidden inside braces.

You can go around this limitation like this:

\documentclass[10pt,a4paper]{article}
\usepackage{color}
\usepackage{nath}
\delimgrowth=1

\begin{document}
$$A \Rightarrow \textcolor{red}{\mbox{(B)}}$$
\end{document}


but I don't know if this is useful for your real case.

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Thanks @egreg . It compiles and looks good. However, This solution turns off nath's automatic parenthesis size adjustment inside the mbox part. This might not be desirable in general –  Abhishek Nov 27 '12 at 23:49
@Abhishek I know. I never use nath because it wants to be too smart. –  egreg Nov 27 '12 at 23:58
Is there any other package that can do automatic nested parenthesis size adjustment for me? –  Abhishek Nov 28 '12 at 0:07
@Abhishek Maybe I'm old fashioned, but I like to choose by myself when growing fences or two story fractions should be used. –  egreg Nov 28 '12 at 0:11