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231 lines
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<h1><a href="../index.html">
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</a></h1>
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<ul><li><a href="../inweb/index.html">inweb</a></li>
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<!--Weave of 'Methods' generated by Inweb-->
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<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="index.html">foundation</a></li><li><a href="index.html#2">Chapter 2: Memory, Streams and Collections</a></li><li><b>Methods</b></li></ul><p class="purpose">General support for something approximating method calls.</p>
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<ul class="toc"><li><a href="2-mth.html#SP1">§1. Method sets</a></li><li><a href="2-mth.html#SP4">§4. Declaring methods</a></li><li><a href="2-mth.html#SP6">§6. Adding methods</a></li><li><a href="2-mth.html#SP7">§7. Calling methods</a></li></ul><hr class="tocbar">
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<p class="inwebparagraph"><a id="SP1"></a><b>§1. Method sets. </b>This section provides a very rudimentary implementation of method calls,
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ordinarily not available in C, but doesn't pretend to offer the full
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functionality of an object-oriented language.
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</p>
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<p class="inwebparagraph">Instead, it's really intended for protocol-based coding patterns. Suppose that
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we have objects of several different structure types, but all of them can
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serve a given purpose — say, all of them contribute an adjective to the
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Inform language. What we want is the ability to take a pointer, which might be
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to an object of any of these types, and to tell the object to do something, or
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ask it a question.
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</p>
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<p class="inwebparagraph">Alternatively, we may have a situation where there are multiple objects of the
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same type which each represent a different way of doing something: for
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example, in the Inweb source code, each different supported programming
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language is represented by an object. These objects need to encapsulate all
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the ways that one language differs from another, and they can do that by
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providing "methods".
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</p>
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<p class="inwebparagraph"><a id="SP2"></a><b>§2. </b>The model is this. If a <span class="extract"><span class="extract-syntax">typedef struct</span></span> definition includes the line
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<span class="extract"><span class="extract-syntax">METHOD_CALLS</span></span>, then any instance of that structure can have a queue of
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tagged functions attached to it dynamically: those, we'll call "methods".
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</p>
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<pre class="definitions">
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<span class="definition-keyword">define</span> <span class="constant-syntax">METHOD_CALLS</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">method_set</span><span class="plain-syntax"> *</span><span class="identifier-syntax">methods</span><span class="plain-syntax">;</span>
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<span class="definition-keyword">define</span> <span class="identifier-syntax">ENABLE_METHOD_CALLS</span><span class="plain-syntax">(</span><span class="identifier-syntax">obj</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">obj</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax"> = </span><a href="2-mth.html#SP3" class="function-link"><span class="function-syntax">Methods::new_set</span></a><span class="plain-syntax">();</span>
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</pre>
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<p class="inwebparagraph"><a id="SP3"></a><b>§3. </b>A "method set" is simply a linked list of methods:
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</p>
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<pre class="displayed-code all-displayed-code">
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<span class="reserved-syntax">typedef</span><span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">method_set</span><span class="plain-syntax"> {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">first_method</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="constant-syntax">MEMORY_MANAGEMENT</span>
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<span class="plain-syntax">} </span><span class="reserved-syntax">method_set</span><span class="plain-syntax">;</span>
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<span class="reserved-syntax">method_set</span><span class="plain-syntax"> *</span><span class="function-syntax">Methods::new_set</span><button class="popup" onclick="togglePopup('usagePopup1')">...<span class="popuptext" id="usagePopup1">Usage of <b>Methods::new_set</b>:<br><a href="2-mth.html#SP2">§2</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">void</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">method_set</span><span class="plain-syntax"> *</span><span class="identifier-syntax">S</span><span class="plain-syntax"> = </span><span class="identifier-syntax">CREATE</span><span class="plain-syntax">(</span><span class="reserved-syntax">method_set</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">S</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">return</span><span class="plain-syntax"> </span><span class="identifier-syntax">S</span><span class="plain-syntax">;</span>
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<span class="plain-syntax">}</span>
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</pre><ul class="endnotetexts"><li>The structure method_set is private to this section.</li></ul><p class="inwebparagraph"><a id="SP4"></a><b>§4. Declaring methods. </b>Each method is a function, though we don't know its type — which is why we
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resort to the desperate measure of storing it as a <span class="extract"><span class="extract-syntax">void *</span></span> — with an ID
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number attached to it. IDs should be from the <span class="extract"><span class="extract-syntax">*_MTID</span></span> enumeration set.
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</p>
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<pre class="definitions">
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<span class="definition-keyword">enum</span> <span class="constant-syntax">UNUSED_METHOD_ID_MTID</span><span class="plain-syntax"> </span><span class="identifier-syntax">from</span><span class="plain-syntax"> </span><span class="constant-syntax">1</span>
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</pre>
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<p class="inwebparagraph"><a id="SP5"></a><b>§5. </b>The type of a method must neverthess be specified, and we do it with one
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of two macros: one for methods returning an integer, one for void methods,
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i.e., those returning no value.
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</p>
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<p class="inwebparagraph">What these do is to use typedef to give the name <span class="extract"><span class="extract-syntax">X_type</span></span> to the type of all
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functions sharing the method ID <span class="extract"><span class="extract-syntax">X</span></span>.
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</p>
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<pre class="definitions">
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<span class="definition-keyword">define</span> <span class="identifier-syntax">IMETHOD_TYPE</span><span class="plain-syntax">(</span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">...)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">typedef</span><span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> (*</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">)(</span><span class="identifier-syntax">args</span><span class="plain-syntax">);</span>
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<span class="definition-keyword">define</span> <span class="identifier-syntax">VMETHOD_TYPE</span><span class="plain-syntax">(</span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">...)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">typedef</span><span class="plain-syntax"> </span><span class="reserved-syntax">void</span><span class="plain-syntax"> (*</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">)(</span><span class="identifier-syntax">args</span><span class="plain-syntax">);</span>
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</pre>
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<pre class="displayed-code all-displayed-code">
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<span class="identifier-syntax">IMETHOD_TYPE</span><span class="plain-syntax">(</span><span class="constant-syntax">UNUSED_METHOD_ID_MTID</span><span class="plain-syntax">, </span><span class="reserved-syntax">text_stream</span><span class="plain-syntax"> *</span><span class="identifier-syntax">example</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">wont_be_used</span><span class="plain-syntax">)</span>
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</pre><p class="inwebparagraph"><a id="SP6"></a><b>§6. Adding methods. </b>Provided a function has the right type for the ID we're using, we can now
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attach it to an object with a method set, using the <span class="extract"><span class="extract-syntax">METHOD_ADD</span></span> macro.
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(If the type is wrong, the C compiler will throw errors here.)
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</p>
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<pre class="definitions">
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<span class="definition-keyword">define</span> <span class="identifier-syntax">METHOD_ADD</span><span class="plain-syntax">(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">func</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><a href="2-mth.html#SP6" class="function-link"><span class="function-syntax">Methods::add</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">, (</span><span class="reserved-syntax">void</span><span class="plain-syntax"> *) &</span><span class="identifier-syntax">func</span><span class="plain-syntax">);</span>
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</pre>
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<pre class="displayed-code all-displayed-code">
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<span class="reserved-syntax">typedef</span><span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">method</span><span class="plain-syntax"> {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">method_id</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">void</span><span class="plain-syntax"> *</span><span class="identifier-syntax">method_function</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">next_method</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="constant-syntax">MEMORY_MANAGEMENT</span>
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<span class="plain-syntax">} </span><span class="reserved-syntax">method</span><span class="plain-syntax">;</span>
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<span class="reserved-syntax">void</span><span class="plain-syntax"> </span><span class="function-syntax">Methods::add</span><button class="popup" onclick="togglePopup('usagePopup2')">...<span class="popuptext" id="usagePopup2">Usage of <b>Methods::add</b>:<br>none</span></button><span class="plain-syntax">(</span><span class="reserved-syntax">method_set</span><span class="plain-syntax"> *</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">ID</span><span class="plain-syntax">, </span><span class="reserved-syntax">void</span><span class="plain-syntax"> *</span><span class="identifier-syntax">function</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">CREATE</span><span class="plain-syntax">(</span><span class="reserved-syntax">method</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> = </span><span class="identifier-syntax">ID</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_function</span><span class="plain-syntax"> = </span><span class="identifier-syntax">function</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">S</span><span class="plain-syntax">-></span><span class="identifier-syntax">first_method</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) </span><span class="identifier-syntax">S</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">existing</span><span class="plain-syntax"> = </span><span class="identifier-syntax">S</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">while</span><span class="plain-syntax"> ((</span><span class="identifier-syntax">existing</span><span class="plain-syntax">) && (</span><span class="identifier-syntax">existing</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)) </span><span class="identifier-syntax">existing</span><span class="plain-syntax"> = </span><span class="identifier-syntax">existing</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">existing</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax">}</span>
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<span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="function-syntax">Methods::provided</span><button class="popup" onclick="togglePopup('usagePopup3')">...<span class="popuptext" id="usagePopup3">Usage of <b>Methods::provided</b>:<br>none</span></button><span class="plain-syntax">(</span><span class="reserved-syntax">method_set</span><span class="plain-syntax"> *</span><span class="identifier-syntax">S</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">ID</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">S</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="constant-syntax">FALSE</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">S</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> == </span><span class="identifier-syntax">ID</span><span class="plain-syntax">)</span>
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<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>
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<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>
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<span class="plain-syntax">}</span>
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</pre><ul class="endnotetexts"><li>The structure method is private to this section.</li></ul><p class="inwebparagraph"><a id="SP7"></a><b>§7. Calling methods. </b>Method calls are also done with a macro, but it has to come in four variants:
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</p>
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</li><li>(a) <span class="extract"><span class="extract-syntax">IMETHOD_CALL</span></span> for a method taking arguments and returning an <span class="extract"><span class="extract-syntax">int</span></span>,
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</li><li>(b) <span class="extract"><span class="extract-syntax">IMETHOD_CALLV</span></span> for a method without arguments which returns an <span class="extract"><span class="extract-syntax">int</span></span>,
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</li><li>(c) <span class="extract"><span class="extract-syntax">VMETHOD_CALL</span></span> for a method taking arguments and returning nothing,
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</li><li>(d) <span class="extract"><span class="extract-syntax">VMETHOD_CALLV</span></span> for a method without arguments which returns nothing.
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</li></ul>
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<p class="inwebparagraph">For example:
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</p>
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<pre class="displayed-code all-displayed-code">
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<span class="plain-syntax"> </span><span class="identifier-syntax">IMETHOD_CALL</span><span class="plain-syntax">(</span><span class="identifier-syntax">some_object</span><span class="plain-syntax">, </span><span class="constant-syntax">UNUSED_METHOD_ID_MTID</span><span class="plain-syntax">, </span><span class="identifier-syntax">I</span><span class="string-syntax">"Hello"</span><span class="plain-syntax">, </span><span class="constant-syntax">17</span><span class="plain-syntax">)</span>
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</pre>
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<p class="inwebparagraph">Note that it's entirely possible for the <span class="extract"><span class="extract-syntax">upon</span></span> object to have multiple methods
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added for the same ID — or none. In the <span class="extract"><span class="extract-syntax">V</span></span> (void) cases, what we then do is
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to call each of them in turn. In the <span class="extract"><span class="extract-syntax">I</span></span> (int) cases, we call each in turn, but
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stop the moment any of them returns something other than <span class="extract"><span class="extract-syntax">FALSE</span></span>, and then
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we put that value into the specified result variable <span class="extract"><span class="extract-syntax">rval</span></span>.
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</p>
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<p class="inwebparagraph">If <span class="extract"><span class="extract-syntax">some_object</span></span> has no methods for the given ID, then nothing happens, and
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in the <span class="extract"><span class="extract-syntax">I</span></span> case, the return value is <span class="extract"><span class="extract-syntax">FALSE</span></span>.
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</p>
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<p class="inwebparagraph">It will, however, produce a compilation error if <span class="extract"><span class="extract-syntax">some_object</span></span> is not a pointer
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to a structure which has <span class="extract"><span class="extract-syntax">METHOD_CALLS</span></span> as part of its definition.
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</p>
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<pre class="definitions">
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<span class="definition-keyword">define</span> <span class="identifier-syntax">IMETHOD_CALL</span><span class="plain-syntax">(</span><span class="identifier-syntax">rval</span><span class="plain-syntax">, </span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">...) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">rval</span><span class="plain-syntax"> = </span><span class="constant-syntax">FALSE</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">upon</span><span class="plain-syntax">?(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">):</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> == </span><span class="identifier-syntax">id</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax"> = (*((</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">) (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_function</span><span class="plain-syntax">)))(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">rval</span><span class="plain-syntax"> = </span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax">}</span>
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<span class="definition-keyword">define</span> <span class="identifier-syntax">IMETHOD_CALLV</span><span class="plain-syntax">(</span><span class="identifier-syntax">rval</span><span class="plain-syntax">, </span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">rval</span><span class="plain-syntax"> = </span><span class="constant-syntax">FALSE</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">upon</span><span class="plain-syntax">?(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">):</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> == </span><span class="identifier-syntax">id</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax"> = (*((</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">) (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_function</span><span class="plain-syntax">)))(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">);</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax">) {</span>
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<span class="plain-syntax"> </span><span class="identifier-syntax">rval</span><span class="plain-syntax"> = </span><span class="identifier-syntax">method_rval_</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">break</span><span class="plain-syntax">;</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax"> }</span>
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<span class="plain-syntax">}</span>
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<span class="definition-keyword">define</span> <span class="identifier-syntax">VMETHOD_CALL</span><span class="plain-syntax">(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">...)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">upon</span><span class="plain-syntax">?(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">):</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> == </span><span class="identifier-syntax">id</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> (*((</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">) (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_function</span><span class="plain-syntax">)))(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">args</span><span class="plain-syntax">);</span>
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<span class="definition-keyword">define</span> <span class="identifier-syntax">VMETHOD_CALLV</span><span class="plain-syntax">(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">, </span><span class="identifier-syntax">id</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="reserved-syntax">method</span><span class="plain-syntax"> *</span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">upon</span><span class="plain-syntax">?(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">-></span><span class="identifier-syntax">methods</span><span class="plain-syntax">-></span><span class="element-syntax">first_method</span><span class="plain-syntax">):</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax">; </span><span class="identifier-syntax">M</span><span class="plain-syntax"> = </span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">next_method</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_id</span><span class="plain-syntax"> == </span><span class="identifier-syntax">id</span><span class="plain-syntax">)</span>
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<span class="plain-syntax"> (*((</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_type</span><span class="plain-syntax">) (</span><span class="identifier-syntax">M</span><span class="plain-syntax">-></span><span class="element-syntax">method_function</span><span class="plain-syntax">)))(</span><span class="identifier-syntax">upon</span><span class="plain-syntax">);</span>
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</pre>
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