How to change font-size for a grammar declaration

Question

I have a grammar declaration like this:

\documentclass[12pt,a4paper]{report}
\usepackage{syntax}
\begin{document}
...
    \begin{figure}[h!]
        \begin{grammar}
            <A> ::= `<--' <B> <C> `-->'

            <B> ::= <D>

            ...
        \end{grammar}
        \caption{A sample grammar}
        \label{fig:sample-grammar}
    \end{figure}
...
\end{document}

LaTeX uses a superfluously large font to render it and some lines do not even fit on the page and need to be wrapped, which has a bad impact on clarity.

How do I change font-size only for the grammar?

Answer 1

Use \AtBeginEnvironment from etoolbox. But, please, always add a complete example with all packages needed. I'm guessing you're using syntax, as I don't know other packages that provide a grammar environment.

\documentclass{article}
\usepackage{syntax,etoolbox}
\AtBeginEnvironment{grammar}{\small}
\begin{document}
Some text before and
some text before and
some text before and
some text before and
some text before and
some text before and
some text before and
some text before
\begin{figure}[!htp]
    \begin{grammar}
        <A> ::= `<--' <B> <C> `-->'

        <B> ::= <D>

    \end{grammar}
    \caption{A sample grammar}
    \label{fig:sample-grammar}
\end{figure}
\end{document}

Don't use the [h!] option alone for the figure environment. You're basically telling LaTeX to run out of space if one of the figures can't be placed where you'd like it to be.