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<title>6.12 Grammar Production Displays
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<H2><A NAME=
"SECTION0007120000000000000000"></A><A NAME=
"grammar-displays"></A>
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
<dt><tt>\begin{
<b class='environment'
>productionlist
</b>}
</tt>
<tt>[
</tt><var>language
</var><tt>]
</tt>
<br /><tt>\end{
<b class='environment'
>productionlist
</b>}
</tt></dt>
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
<var>language
</var> 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
<dt><b><tt class='macro'
>\production
</tt></b>
<tt>{
</tt><var>name
</var><tt>}
</tt><tt>{
</tt><var>definition
</var><tt>}
</tt></dt>
A production rule in the grammar. The rule defines the symbol
<var>name
</var> to be
<var>definition
</var>.
<var>name
</var> should not
contain any markup, and the use of hyphens in a document which
supports more than one grammar is undefined.
<var>definition
</var>
may contain
<tt class='macro'
>\token
</tt> macros and any additional content
needed to describe the grammatical model of
<var>symbol
</var>. Only
one
<tt class='macro'
>\production
</tt> may be used to define a symbol --
multiple definitions are not allowed.
<dt><b><tt class='macro'
>\token
</tt></b>
<tt>{
</tt><var>name
</var><tt>}
</tt></dt>
The name of a symbol defined by a
<tt class='macro'
>\production
</tt> macro, used
in the
<var>definition
</var> of a symbol. Where possible, this will
be rendered as a hyperlink to the definition of the symbol
Note that the entire grammar does not need to be defined in a
single
<tt class='environment'
>\productionlist
</tt> environment; any number of
groupings may be used to describe the grammar. Every use of the
<tt class='macro'
>\token
</tt> must correspond to a
<tt class='macro'
>\production
</tt>.
The following is an example taken from the
href=
"../ref/identifiers.html"
title=
"Python Reference Manual"
>Python Reference Manual
</a></em>:
<div class=
"verbatim"><pre>
{(\token{letter}|
"_") (\token{letter} | \token{digit} |
"_")*}
{\token{lowercase} | \token{uppercase}}
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<span class=
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2.4.2, documentation updated on
28 September
2005.
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