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doc/us/examples.html

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2 "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
3 <html>
4 <head>
5 <title>LuaExpat: XML Expat parsing for the Lua programming language</title>
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11 <div id="container">
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14 <div id="product_logo"><a href="http://www.keplerproject.org">
15 <img alt="LuaExpat logo" src="luaexpat.png"/>
16 </a></div>
17 <div id="product_name"><big><strong>LuaExpat</strong></big></div>
18 <div id="product_description">XML Expat parsing for the Lua programming language</div>
19 </div> <!-- id="product" -->
20
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22
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24 <h1>LuaExpat</h1>
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39 <li><a href="manual.html#introduction">Introduction</a></li>
40 <li><a href="manual.html#installation">Installation</a></li>
41 <li><a href="manual.html#parser">Parser Objects</a></li>
42 </ul>
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44 <li><strong>Examples</strong></li>
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56 <div id="content">
57
58 <h2><a name="examples"></a>Examples</h2>
59
60 <p>The code excerpt below creates a parser with 2 callbacks and
61 feeds a test string to it. The parsing of the test string triggers
62 the callbacks, printing the results.</p>
63
64 <pre class="example">
65 require"lxp"
66
67 local count = 0
68 callbacks = {
69 StartElement = function (parser, name)
70 io.write("+ ", string.rep(" ", count), name, "\n")
71 count = count + 1
72 end,
73 EndElement = function (parser, name)
74 count = count - 1
75 io.write("- ", string.rep(" ", count), name, "\n")
76 end
77 }
78
79 p = lxp.new(callbacks)
80
81 for l in io.lines() do -- iterate lines
82 p:parse(l) -- parses the line
83 p:parse("\n") -- parses the end of line
84 end
85 p:parse() -- finishes the document
86 p:close() -- closes the parser
87 </pre>
88
89 <p>For a test string like</p>
90
91 <pre class="example">
92 &lt;elem1&gt;
93 text
94 &lt;elem2/&gt;
95 more text
96 &lt;/elem1&gt;
97 </pre>
98
99 <p>The example would print</p>
100
101 <pre class="example">
102 + elem1
103 + elem2
104 - elem2
105 - elem1
106 </pre>
107
108 <p>Note that the text parts are not handled since the corresponding
109 callback (<em>CharacterData</em>) has not been defined. Also note
110 that defining this callback after the call to lxp.new would make no
111 difference. But had the callback table been defined as</p>
112
113 <pre class="example">
114 callbacks = {
115 StartElement = function (parser, name)
116 io.write("+ ", string.rep(" ", count), name, "\n")
117 count = count + 1
118 end,
119 EndElement = function (parser, name)
120 count = count - 1
121 io.write("- ", string.rep(" ", count), name, "\n")
122 end,
123 CharacterData = function (parser, string)
124 io.write("* ", string.rep(" ", count), string, "\n")
125 end
126 }
127 </pre>
128
129 <p>The results would have been</p>
130
131 <pre class="example">
132 + elem1
133 * text
134 + elem2
135 - elem2
136 * more text
137 - elem1
138 </pre>
139
140 <p>Another example would be the use of <em>false</em> as a
141 placeholder for the callback. Suppose that we would like to print
142 only the text associated with <em>elem2</em> elements and that the
143 XML sample is</p>
144
145 <pre class="example">
146 &lt;elem1&gt;
147 text
148 &lt;elem2&gt;
149 inside text
150 &lt;/elem2&gt;
151 more text
152 &lt;/elem1&gt;
153 </pre>
154
155 <p>We could define the new callback table as</p>
156
157 <pre class="example">
158 callbacks = {
159 StartElement = function (parser, name)
160 if name == "elem2" then
161 -- redefines CharacterData behaviour
162 callbacks.CharacterData = function (parser, string)
163 io.write(string, "\n")
164 end
165 end
166 end,
167
168 EndElement = function (parser, name)
169 if name == "elem2" then
170 callbacks.CharacterData = false -- restores placeholder
171 end
172 end,
173
174 CharacterData = false -- placeholder
175 }
176 </pre>
177
178 <p>The results would have been</p>
179
180 <pre class="example">
181 inside text
182 </pre>
183
184 <p>Note that this example assumes no other elements are present
185 inside elem2 tags.</p>
186
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