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| 53 | <H2><A NAME="SECTION0007120000000000000000"></A><A NAME="grammar-displays"></A> |
| 54 | <BR> |
| 55 | 6.12 Grammar Production Displays |
| 56 | </H2> |
| 57 | |
| 58 | <P> |
| 59 | Special markup is available for displaying the productions of a |
| 60 | formal grammar. The markup is simple and does not attempt to |
| 61 | model all aspects of BNF (or any derived forms), but provides |
| 62 | enough to allow context-free grammars to be displayed in a way |
| 63 | that causes uses of a symbol to be rendered as hyperlinks to the |
| 64 | definition of the symbol. There is one environment and a pair of |
| 65 | macros: |
| 66 | |
| 67 | <P> |
| 68 | |
| 69 | <dl class='envdesc'> |
| 70 | <dt><tt>\begin{<b class='environment'>productionlist</b>}</tt> |
| 71 | <tt>[</tt><var>language</var><tt>]</tt> |
| 72 | <br /><tt>\end{<b class='environment'>productionlist</b>}</tt></dt> |
| 73 | <dd> |
| 74 | This environment is used to enclose a group of productions. The |
| 75 | two macros are only defined within this environment. If a |
| 76 | document describes more than one language, the optional parameter |
| 77 | <var>language</var> should be used to distinguish productions between |
| 78 | languages. The value of the parameter should be a short name |
| 79 | that can be used as part of a filename; colons or other |
| 80 | characters that can't be used in filename across platforms |
| 81 | should be included. |
| 82 | </dd></dl> |
| 83 | |
| 84 | <P> |
| 85 | |
| 86 | <dl class='macrodesc'> |
| 87 | <dt><b><tt class='macro'>\production</tt></b> |
| 88 | <tt>{</tt><var>name</var><tt>}</tt><tt>{</tt><var>definition</var><tt>}</tt></dt> |
| 89 | <dd> |
| 90 | A production rule in the grammar. The rule defines the symbol |
| 91 | <var>name</var> to be <var>definition</var>. <var>name</var> should not |
| 92 | contain any markup, and the use of hyphens in a document which |
| 93 | supports more than one grammar is undefined. <var>definition</var> |
| 94 | may contain <tt class='macro'>\token</tt> macros and any additional content |
| 95 | needed to describe the grammatical model of <var>symbol</var>. Only |
| 96 | one <tt class='macro'>\production</tt> may be used to define a symbol -- |
| 97 | multiple definitions are not allowed. |
| 98 | </dd></dl> |
| 99 | |
| 100 | <P> |
| 101 | |
| 102 | <dl class='macrodesc'> |
| 103 | <dt><b><tt class='macro'>\token</tt></b> |
| 104 | <tt>{</tt><var>name</var><tt>}</tt></dt> |
| 105 | <dd> |
| 106 | The name of a symbol defined by a <tt class='macro'>\production</tt> macro, used |
| 107 | in the <var>definition</var> of a symbol. Where possible, this will |
| 108 | be rendered as a hyperlink to the definition of the symbol |
| 109 | <var>name</var>. |
| 110 | </dd></dl> |
| 111 | |
| 112 | <P> |
| 113 | Note that the entire grammar does not need to be defined in a |
| 114 | single <tt class='environment'>\productionlist</tt> environment; any number of |
| 115 | groupings may be used to describe the grammar. Every use of the |
| 116 | <tt class='macro'>\token</tt> must correspond to a <tt class='macro'>\production</tt>. |
| 117 | |
| 118 | <P> |
| 119 | The following is an example taken from the |
| 120 | <em class="citetitle"><a |
| 121 | href="../ref/identifiers.html" |
| 122 | title="Python Reference Manual" |
| 123 | >Python Reference Manual</a></em>: |
| 124 | |
| 125 | <P> |
| 126 | <div class="verbatim"><pre> |
| 127 | \begin{productionlist} |
| 128 | \production{identifier} |
| 129 | {(\token{letter}|"_") (\token{letter} | \token{digit} | "_")*} |
| 130 | \production{letter} |
| 131 | {\token{lowercase} | \token{uppercase}} |
| 132 | \production{lowercase} |
| 133 | {"a"..."z"} |
| 134 | \production{uppercase} |
| 135 | {"A"..."Z"} |
| 136 | \production{digit} |
| 137 | {"0"..."9"} |
| 138 | \end{productionlist} |
| 139 | </pre></div> |
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