158 lines
8.8 KiB
HTML
158 lines
8.8 KiB
HTML
<!DOCTYPE html>
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<html>
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<!-- This manual documents Guile version 3.0.10.
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Copyright (C) 1996-1997, 2000-2005, 2009-2023 Free Software Foundation,
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Inc.
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Copyright (C) 2021 Maxime Devos
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Copyright (C) 2024 Tomas Volf
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Permission is granted to copy, distribute and/or modify this document
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under the terms of the GNU Free Documentation License, Version 1.3 or
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any later version published by the Free Software Foundation; with no
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Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A
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copy of the license is included in the section entitled "GNU Free
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Documentation License." -->
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<title>Transforming SXML (Guile Reference Manual)</title>
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<meta name="description" content="Transforming SXML (Guile Reference Manual)">
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<link href="index.html" rel="start" title="Top">
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<link href="Concept-Index.html" rel="index" title="Concept Index">
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<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents">
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<link href="SXML.html" rel="up" title="SXML">
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<link href="SXML-Tree-Fold.html" rel="next" title="SXML Tree Fold">
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<link href="SSAX.html" rel="prev" title="SSAX">
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<body lang="en">
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<div class="subsection-level-extent" id="Transforming-SXML">
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<div class="nav-panel">
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<p>
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Next: <a href="SXML-Tree-Fold.html" accesskey="n" rel="next">SXML Tree Fold</a>, Previous: <a href="SSAX.html" accesskey="p" rel="prev">SSAX: A Functional XML Parsing Toolkit</a>, Up: <a href="SXML.html" accesskey="u" rel="up">SXML</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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<hr>
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<h4 class="subsection" id="Transforming-SXML-1"><span>7.21.4 Transforming SXML<a class="copiable-link" href="#Transforming-SXML-1"> ¶</a></span></h4>
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<ul class="mini-toc">
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<li><a href="#Overview" accesskey="1">Overview</a></li>
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<li><a href="#Usage-1" accesskey="2">Usage</a></li>
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</ul>
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<div class="subsubsection-level-extent" id="Overview">
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<h4 class="subsubsection"><span>7.21.4.1 Overview<a class="copiable-link" href="#Overview"> ¶</a></span></h4>
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<h3 class="heading" id="SXML-expression-tree-transformers"><span>SXML expression tree transformers<a class="copiable-link" href="#SXML-expression-tree-transformers"> ¶</a></span></h3>
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<h4 class="subheading" id="Pre_002dPost_002dorder-traversal-of-a-tree-and-creation-of-a-new-tree"><span>Pre-Post-order traversal of a tree and creation of a new tree<a class="copiable-link" href="#Pre_002dPost_002dorder-traversal-of-a-tree-and-creation-of-a-new-tree"> ¶</a></span></h4>
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<div class="example smallexample">
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<pre class="example-preformatted">pre-post-order:: <tree> x <bindings> -> <new-tree>
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</pre></div>
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<p>where
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</p>
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<div class="example smallexample">
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<pre class="example-preformatted"> <bindings> ::= (<binding> ...)
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<binding> ::= (<trigger-symbol> *preorder* . <handler>) |
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(<trigger-symbol> *macro* . <handler>) |
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(<trigger-symbol> <new-bindings> . <handler>) |
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(<trigger-symbol> . <handler>)
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<trigger-symbol> ::= XMLname | *text* | *default*
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<handler> :: <trigger-symbol> x [<tree>] -> <new-tree>
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</pre></div>
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<p>The <code class="code">pre-post-order</code> function, in the <code class="code">(sxml transform)</code>
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module, visits the nodes and nodelists pre-post-order (depth-first).
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For each <code class="code"><Node></code> of the form <code class="code">(<var class="var">name</var> <Node> ...)</code>, it
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looks up an association with the given <var class="var">name</var> among its
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<var class="var"><bindings></var>. If failed, <code class="code">pre-post-order</code> tries to locate a
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<code class="code">*default*</code> binding. It’s an error if the latter attempt fails as
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well. Having found a binding, the <code class="code">pre-post-order</code> function first
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checks to see if the binding is of the form
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</p>
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<div class="example smallexample">
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<pre class="example-preformatted"> (<trigger-symbol> *preorder* . <handler>)
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</pre></div>
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<p>If it is, the handler is ’applied’ to the current node. Otherwise, the
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pre-post-order function first calls itself recursively for each child of
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the current node, with <var class="var"><new-bindings></var> prepended to the
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<var class="var"><bindings></var> in effect. The result of these calls is passed to the
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<var class="var"><handler></var> (along with the head of the current <var class="var"><Node></var>). To be
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more precise, the handler is _applied_ to the head of the current node
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and its processed children. The result of the handler, which should also
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be a <code class="code"><tree></code>, replaces the current <var class="var"><Node></var>. If the current
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<var class="var"><Node></var> is a text string or other atom, a special binding with a
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symbol <code class="code">*text*</code> is looked up.
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</p>
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<p>A binding can also be of a form
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</p>
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<div class="example smallexample">
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<pre class="example-preformatted"> (<trigger-symbol> *macro* . <handler>)
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</pre></div>
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<p>This is equivalent to <code class="code">*preorder*</code> described above. However, the
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result is re-processed again, with the current stylesheet.
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</p>
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</div>
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<div class="subsubsection-level-extent" id="Usage-1">
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<h4 class="subsubsection"><span>7.21.4.2 Usage<a class="copiable-link" href="#Usage-1"> ¶</a></span></h4>
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<dl class="first-deffn">
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<dt class="deffn" id="index-SRV_003asend_002dreply"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">SRV:send-reply</strong> <var class="def-var-arguments">. fragments</var><a class="copiable-link" href="#index-SRV_003asend_002dreply"> ¶</a></span></dt>
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<dd><p>Output the <var class="var">fragments</var> to the current output port.
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</p>
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<p>The fragments are a list of strings, characters, numbers, thunks,
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<code class="code">#f</code>, <code class="code">#t</code> – and other fragments. The function traverses the
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tree depth-first, writes out strings and characters, executes thunks,
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and ignores <code class="code">#f</code> and <code class="code">'()</code>. The function returns <code class="code">#t</code> if
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anything was written at all; otherwise the result is <code class="code">#f</code> If
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<code class="code">#t</code> occurs among the fragments, it is not written out but causes
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the result of <code class="code">SRV:send-reply</code> to be <code class="code">#t</code>.
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</p></dd></dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-foldts"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">foldts</strong> <var class="def-var-arguments">fdown fup fhere seed tree</var><a class="copiable-link" href="#index-foldts"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-post_002dorder"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">post-order</strong> <var class="def-var-arguments">tree bindings</var><a class="copiable-link" href="#index-post_002dorder"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-pre_002dpost_002dorder"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">pre-post-order</strong> <var class="def-var-arguments">tree bindings</var><a class="copiable-link" href="#index-pre_002dpost_002dorder"> ¶</a></span></dt>
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</dl>
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<dl class="first-deffn">
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<dt class="deffn" id="index-replace_002drange"><span class="category-def">Scheme Procedure: </span><span><strong class="def-name">replace-range</strong> <var class="def-var-arguments">beg-pred end-pred forest</var><a class="copiable-link" href="#index-replace_002drange"> ¶</a></span></dt>
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</dl>
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</div>
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</div>
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<hr>
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<div class="nav-panel">
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<p>
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Next: <a href="SXML-Tree-Fold.html">SXML Tree Fold</a>, Previous: <a href="SSAX.html">SSAX: A Functional XML Parsing Toolkit</a>, Up: <a href="SXML.html">SXML</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Concept-Index.html" title="Index" rel="index">Index</a>]</p>
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</div>
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</body>
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</html>
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