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6.12 Grammar Production Displays

Special markup is available for displaying the productions of a formal grammar. The markup is simple and does not attempt to model all aspects of BNF (or any derived forms), but provides enough to allow context-free grammars to be displayed in a way that causes uses of a symbol to be rendered as hyperlinks to the definition of the symbol. There is one environment and a pair of macros:

`\begin{productionlist}` `[`language`]`
`\end{productionlist}`
  This environment is used to enclose a group of productions. The two macros are only defined within this environment. If a document describes more than one language, the optional parameter language should be used to distinguish productions between languages. The value of the parameter should be a short name that can be used as part of a filename; colons or other characters that can't be used in filename across platforms should be included.

`\production` `{`name`}``{`definition`}`
  A production rule in the grammar. The rule defines the symbol name to be definition. name should not contain any markup, and the use of hyphens in a document which supports more than one grammar is undefined. definition may contain `\token` macros and any additional content needed to describe the grammatical model of symbol. Only one `\production` may be used to define a symbol -- multiple definitions are not allowed.

`\token` `{`name`}`
  The name of a symbol defined by a `\production` macro, used in the definition of a symbol. Where possible, this will be rendered as a hyperlink to the definition of the symbol name.

Note that the entire grammar does not need to be defined in a single `\productionlist` environment; any number of groupings may be used to describe the grammar. Every use of the `\token` must correspond to a `\production`.

The following is an example taken from the Python Reference Manual:

    \begin{productionlist}
      \production{identifier}
                 {(\token{letter}|"_") (\token{letter} | \token{digit} | "_")*}
      \production{letter}
                 {\token{lowercase} | \token{uppercase}}
      \production{lowercase}
                 {"a"..."z"}
      \production{uppercase}
                 {"A"..."Z"}
      \production{digit}
                 {"0"..."9"}
    \end{productionlist}