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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Context Symbols</title>
<link href="../docs-assets/Breadcrumbs.css" rel="stylesheet" rev="stylesheet" type="text/css">
<meta name="viewport" content="width=device-width initial-scale=1">
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<script>
function togglePopup(material_id) {
var popup = document.getElementById(material_id);
popup.classList.toggle("show");
}
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<h1><a href="../index.html">
<img src="../docs-assets/Inform.png" height=72">
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</nav>
<main role="main">
<!--Weave of 'Context Symbols' generated by Inweb-->
<div class="breadcrumbs">
<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="index.html">indoc</a></li><li><a href="index.html#1">Chapter 1: Setting Up</a></li><li><b>Context Symbols</b></li></ul></div>
<p class="purpose">Provides conditional rendering of text, depending on context.</p>
<ul class="toc"><li><a href="1-cs.html#SP1">&#167;1. About symbols</a></li><li><a href="1-cs.html#SP2">&#167;2. Starting up</a></li><li><a href="1-cs.html#SP3">&#167;3. Making and unmaking</a></li><li><a href="1-cs.html#SP4">&#167;4. Testing</a></li></ul><hr class="tocbar">
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. About symbols. </b>Documentation is allowed to contain rawtext which varies depending on the
context: on what platform it's being written for, or what format it is
being rendered to, for example. The context is defined by which symbol
names have been defined.
</p>
<p class="commentary">Symbols are C-like identifiers (alphanumeric or underscored). The symbol has
been declared if and only if it is an existing key for the following hash,
and the associated value is "y".
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">dictionary</span><span class="plain-syntax"> *</span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
</pre>
<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>&#167;2. Starting up. </b>The symbol <span class="extract"><span class="extract-syntax">indoc</span></span> is always defined, so that, in theory, other programs
working on rawtext can distinguish themselves from us (by not defining it).
For example,
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> {^indoc:}You'll probably never see this paragraph.</span>
</pre>
<p class="commentary">provides rawtext visible only if <span class="extract"><span class="extract-syntax">indoc</span></span> isn't the renderer.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::start_up_symbols</span><button class="popup" onclick="togglePopup('usagePopup1')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup1">Usage of <span class="code-font"><span class="function-syntax">Symbols::start_up_symbols</span></span>:<br/>Main - <a href="1-mn.html#SP1_1">&#167;1.1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">void</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><a href="1-cs.html#SP3" class="function-link"><span class="function-syntax">Symbols::declare_symbol</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">I</span><span class="string-syntax">"indoc"</span><span class="plain-syntax">);</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>&#167;3. Making and unmaking. </b></p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::declare_symbol</span><button class="popup" onclick="togglePopup('usagePopup2')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup2">Usage of <span class="code-font"><span class="function-syntax">Symbols::declare_symbol</span></span>:<br/><a href="1-cs.html#SP2">&#167;2</a><br/>Instructions - <a href="1-ins.html#SP5">&#167;5</a>, <a href="1-ins.html#SP3_2">&#167;3.2</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">symbol</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) </span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/2-dct.html#SP2" class="function-link"><span class="function-syntax">Dictionaries::new</span></a><span class="plain-syntax">(10, </span><span class="constant-syntax">TRUE</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">entry</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/2-dct.html#SP9" class="function-link"><span class="function-syntax">Dictionaries::create_text</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax">, </span><span class="identifier-syntax">symbol</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">entry</span><span class="plain-syntax">, </span><span class="identifier-syntax">I</span><span class="string-syntax">"y"</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">SYMBOLS</span><span class="plain-syntax">, </span><span class="string-syntax">"Declaring &lt;%S&gt;\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">symbol</span><span class="plain-syntax">);</span>
<span class="plain-syntax">}</span>
<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::undeclare_symbol</span><button class="popup" onclick="togglePopup('usagePopup3')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup3">Usage of <span class="code-font"><span class="function-syntax">Symbols::undeclare_symbol</span></span>:<br/>Instructions - <a href="1-ins.html#SP5">&#167;5</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">symbol</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">entry</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/2-dct.html#SP10" class="function-link"><span class="function-syntax">Dictionaries::get_text</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax">, </span><span class="identifier-syntax">symbol</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">entry</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) </span><span class="reserved-syntax">return</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">entry</span><span class="plain-syntax">, </span><span class="identifier-syntax">I</span><span class="string-syntax">"n"</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">SYMBOLS</span><span class="plain-syntax">, </span><span class="string-syntax">"Undeclaring &lt;%S&gt;\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">symbol</span><span class="plain-syntax">);</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP4" class="paragraph-anchor"></a><b>&#167;4. Testing. </b>This returns 1 if the current context matches the condition given, and 0
otherwise.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::perform_ifdef</span><button class="popup" onclick="togglePopup('usagePopup4')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup4">Usage of <span class="code-font"><span class="function-syntax">Symbols::perform_ifdef</span></span>:<br/><a href="1-cs.html#SP5_1">&#167;5.1</a>, <a href="1-cs.html#SP5_2">&#167;5.2</a>, <a href="1-cs.html#SP5_3">&#167;5.3</a>, <a href="1-cs.html#SP5_4">&#167;5.4</a><br/>Structural Scan - <a href="2-ss.html#SP5_1">&#167;5.1</a><br/>Rawtext Reader - <a href="2-rr.html#SP4_1">&#167;4.1</a>, <a href="2-rr.html#SP4_6_1">&#167;4.6.1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">cond</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">=0, </span><span class="identifier-syntax">L</span><span class="plain-syntax">=</span><a href="../../../inweb/foundation-module/4-sm.html#SP8" class="function-link"><span class="function-syntax">Str::len</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">); </span><span class="identifier-syntax">i</span><span class="plain-syntax">&lt;</span><span class="identifier-syntax">L</span><span class="plain-syntax">; </span><span class="identifier-syntax">i</span><span class="plain-syntax">++) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">c</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-sm.html#SP13" class="function-link"><span class="function-syntax">Str::get_at</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">i</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="../../../inweb/foundation-module/4-chr.html#SP2" class="function-link"><span class="function-syntax">Characters::is_whitespace</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">c</span><span class="plain-syntax">)) {</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP25" class="function-link"><span class="function-syntax">Str::delete_nth_character</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">i</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">i</span><span class="plain-syntax">--; </span><span class="identifier-syntax">L</span><span class="plain-syntax">--;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">v</span><span class="plain-syntax"> = </span><a href="1-cs.html#SP5" class="function-link"><span class="function-syntax">Symbols::perform_ifdef_inner</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOGIF</span><span class="plain-syntax">(</span><span class="identifier-syntax">SYMBOLS</span><span class="plain-syntax">, </span><span class="string-syntax">"Ifdef &lt;%S&gt; --&gt; %s\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">v</span><span class="plain-syntax">?</span><span class="string-syntax">"yes"</span><span class="plain-syntax">:</span><span class="string-syntax">"no"</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">v</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP5" class="paragraph-anchor"></a><b>&#167;5. </b>There is an expression grammar here, which we apply correctly if the
condition is well-formed; if it's a mess, we try to return 0, but don't go
to any trouble to report errors.
</p>
<p class="commentary">Any condition can be bracketed; otherwise we have the unary operator <span class="extract"><span class="extract-syntax">^</span></span>
(negation), the binary <span class="extract"><span class="extract-syntax">+</span></span> (conjunction), and binary <span class="extract"><span class="extract-syntax">,</span></span> (disjunction),
which associate in that order. An atomic condition is true if and only if
it is a declared symbol. So for example
</p>
<p class="commentary"> ^alpha,beta+gamma
</p>
<p class="commentary">is true if either alpha is undeclared, or if both beta and gamma are declared.
Whereas
</p>
<p class="commentary"> ^(alpha,beta)+gamma
^alpha+^beta+gamma
</p>
<p class="commentary">are both true if alpha and beta are undeclared but gamma is declared.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::perform_ifdef_inner</span><button class="popup" onclick="togglePopup('usagePopup5')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup5">Usage of <span class="code-font"><span class="function-syntax">Symbols::perform_ifdef_inner</span></span>:<br/><a href="1-cs.html#SP4">&#167;4</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">cond</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_1" class="named-paragraph-link"><span class="named-paragraph">Subexpressions can be bracketed</span><span class="named-paragraph-number">5.1</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_2" class="named-paragraph-link"><span class="named-paragraph">The comma operator is left-associative and means or</span><span class="named-paragraph-number">5.2</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_3" class="named-paragraph-link"><span class="named-paragraph">The plus operator is left-associative and means and</span><span class="named-paragraph-number">5.3</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_4" class="named-paragraph-link"><span class="named-paragraph">The caret operator is unary and means not</span><span class="named-paragraph-number">5.4</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_5" class="named-paragraph-link"><span class="named-paragraph">A bare symbol name is true if and only if it is declared</span><span class="named-paragraph-number">5.5</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_6" class="named-paragraph-link"><span class="named-paragraph">The expression is malformed</span><span class="named-paragraph-number">5.6</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP5_1" class="paragraph-anchor"></a><b>&#167;5.1. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Subexpressions can be bracketed</span><span class="named-paragraph-number">5.1</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">match_results</span><span class="plain-syntax"> </span><span class="identifier-syntax">mr</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::create_mr</span></a><span class="plain-syntax">();</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="../../../inweb/foundation-module/4-pm.html#SP10" class="function-link"><span class="function-syntax">Regexp::match</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">L</span><span class="string-syntax">"%((%c*)%)"</span><span class="plain-syntax">)) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax"> = </span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">mr</span><span class="plain-syntax">.</span><span class="element-syntax">exp</span><span class="plain-syntax">[0]);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::dispose_of</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP5_2" class="paragraph-anchor"></a><b>&#167;5.2. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">The comma operator is left-associative and means or</span><span class="named-paragraph-number">5.2</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">k</span><span class="plain-syntax"> = </span><a href="1-cs.html#SP6" class="function-link"><span class="function-syntax">Symbols::find_operator</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="character-syntax">','</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> &gt;= </span><span class="constant-syntax">0</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP15" class="function-link"><span class="function-syntax">Str::truncate</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">, </span><span class="identifier-syntax">k</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy_tail</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">k</span><span class="plain-syntax">+1);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax"> = ((</span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)) || (</span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)));</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">DISCARD_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">DISCARD_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> } </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> == -2) </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_6" class="named-paragraph-link"><span class="named-paragraph">The expression is malformed</span><span class="named-paragraph-number">5.6</span></a></span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP5_3" class="paragraph-anchor"></a><b>&#167;5.3. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">The plus operator is left-associative and means and</span><span class="named-paragraph-number">5.3</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">k</span><span class="plain-syntax"> = </span><a href="1-cs.html#SP6" class="function-link"><span class="function-syntax">Symbols::find_operator</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="character-syntax">'+'</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> &gt;= </span><span class="constant-syntax">0</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">TEMPORARY_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP15" class="function-link"><span class="function-syntax">Str::truncate</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">, </span><span class="identifier-syntax">k</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-sm.html#SP17" class="function-link"><span class="function-syntax">Str::copy_tail</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">k</span><span class="plain-syntax">+1);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax"> = ((</span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)) &amp;&amp; (</span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)));</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">DISCARD_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">L</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">DISCARD_TEXT</span><span class="plain-syntax">(</span><span class="identifier-syntax">R</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> } </span><span class="reserved-syntax">else</span><span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> == -2) </span><span class="named-paragraph-container code-font"><a href="1-cs.html#SP5_6" class="named-paragraph-link"><span class="named-paragraph">The expression is malformed</span><span class="named-paragraph-number">5.6</span></a></span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP5_4" class="paragraph-anchor"></a><b>&#167;5.4. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">The caret operator is unary and means not</span><span class="named-paragraph-number">5.4</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">match_results</span><span class="plain-syntax"> </span><span class="identifier-syntax">mr</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::create_mr</span></a><span class="plain-syntax">();</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="../../../inweb/foundation-module/4-pm.html#SP10" class="function-link"><span class="function-syntax">Regexp::match</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">L</span><span class="string-syntax">"%^(%c*)"</span><span class="plain-syntax">)) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax"> = </span><a href="1-cs.html#SP4" class="function-link"><span class="function-syntax">Symbols::perform_ifdef</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">mr</span><span class="plain-syntax">.</span><span class="element-syntax">exp</span><span class="plain-syntax">[0]);</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::dispose_of</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">rv</span><span class="plain-syntax">?</span><span class="identifier-syntax">FALSE:TRUE</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP5_5" class="paragraph-anchor"></a><b>&#167;5.5. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">A bare symbol name is true if and only if it is declared</span><span class="named-paragraph-number">5.5</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="reserved-syntax">match_results</span><span class="plain-syntax"> </span><span class="identifier-syntax">mr</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::create_mr</span></a><span class="plain-syntax">();</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="../../../inweb/foundation-module/4-pm.html#SP10" class="function-link"><span class="function-syntax">Regexp::match</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">L</span><span class="string-syntax">"%i+"</span><span class="plain-syntax">)) {</span>
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/4-pm.html#SP9" class="function-link"><span class="function-syntax">Regexp::dispose_of</span></a><span class="plain-syntax">(&amp;</span><span class="identifier-syntax">mr</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">entry</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/2-dct.html#SP10" class="function-link"><span class="function-syntax">Dictionaries::get_text</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">defined_symbols</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="../../../inweb/foundation-module/4-sm.html#SP22" class="function-link"><span class="function-syntax">Str::eq_wide_string</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">entry</span><span class="plain-syntax">, </span><span class="identifier-syntax">L</span><span class="string-syntax">"y"</span><span class="plain-syntax">)) </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="constant-syntax">TRUE</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="constant-syntax">FALSE</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP5_6" class="paragraph-anchor"></a><b>&#167;5.6. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">The expression is malformed</span><span class="named-paragraph-number">5.6</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><a href="../../../inweb/foundation-module/3-em.html#SP7" class="function-link"><span class="function-syntax">Errors::with_text</span></a><span class="plain-syntax">(</span><span class="string-syntax">"malformed condition: %S"</span><span class="plain-syntax">, </span><span class="identifier-syntax">cond</span><span class="plain-syntax">); </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="constant-syntax">0</span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="1-cs.html#SP5">&#167;5</a>, <a href="1-cs.html#SP5_2">&#167;5.2</a>, <a href="1-cs.html#SP5_3">&#167;5.3</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP6" class="paragraph-anchor"></a><b>&#167;6. </b>The following looks for a single character <span class="extract"><span class="extract-syntax">op</span></span> in any unbracketed interior
parts of the text <span class="extract"><span class="extract-syntax">cond</span></span>, and looks out for mismatched brackets on the way.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">Symbols::find_operator</span><button class="popup" onclick="togglePopup('usagePopup6')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup6">Usage of <span class="code-font"><span class="function-syntax">Symbols::find_operator</span></span>:<br/><a href="1-cs.html#SP5_2">&#167;5.2</a>, <a href="1-cs.html#SP5_3">&#167;5.3</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">op</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">bl</span><span class="plain-syntax"> = </span><span class="constant-syntax">0</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">k</span><span class="plain-syntax"> = </span><span class="constant-syntax">0</span><span class="plain-syntax">, </span><span class="identifier-syntax">L</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-sm.html#SP8" class="function-link"><span class="function-syntax">Str::len</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">); </span><span class="identifier-syntax">k</span><span class="plain-syntax"> &lt; </span><span class="identifier-syntax">L</span><span class="plain-syntax">; </span><span class="identifier-syntax">k</span><span class="plain-syntax">++) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">ch</span><span class="plain-syntax"> = </span><a href="../../../inweb/foundation-module/4-sm.html#SP13" class="function-link"><span class="function-syntax">Str::get_at</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">cond</span><span class="plain-syntax">, </span><span class="identifier-syntax">k</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">ch</span><span class="plain-syntax"> == </span><span class="character-syntax">'('</span><span class="plain-syntax">) </span><span class="identifier-syntax">bl</span><span class="plain-syntax">++;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">ch</span><span class="plain-syntax"> == </span><span class="character-syntax">')'</span><span class="plain-syntax">) </span><span class="identifier-syntax">bl</span><span class="plain-syntax">--;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">bl</span><span class="plain-syntax"> &lt; </span><span class="constant-syntax">0</span><span class="plain-syntax">) </span><span class="reserved-syntax">return</span><span class="plain-syntax"> -2; </span><span class="comment-syntax"> Too many close brackets</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">bl</span><span class="plain-syntax"> == </span><span class="constant-syntax">0</span><span class="plain-syntax">) &amp;&amp; (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> &gt; </span><span class="constant-syntax">0</span><span class="plain-syntax">) &amp;&amp; (</span><span class="identifier-syntax">k</span><span class="plain-syntax"> &lt; </span><span class="identifier-syntax">L</span><span class="plain-syntax"> - </span><span class="constant-syntax">1</span><span class="plain-syntax">) &amp;&amp; (</span><span class="identifier-syntax">ch</span><span class="plain-syntax"> == </span><span class="identifier-syntax">op</span><span class="plain-syntax">)) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">k</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">bl</span><span class="plain-syntax"> != </span><span class="constant-syntax">0</span><span class="plain-syntax">) </span><span class="reserved-syntax">return</span><span class="plain-syntax"> -2; </span><span class="comment-syntax"> Too many open brackets</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> -1; </span><span class="comment-syntax"> Not found</span>
<span class="plain-syntax">}</span>
</pre>
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