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<div class="breadcrumbs">
<ul class="crumbs"><li><a href="../index.html">Home</a></li><li><a href="../compiler.html">Inform7 Modules</a></li><li><a href="index.html">core</a></li><li><a href="index.html#16">Chapter 16: Inference and Model</a></li><li><b>Property Permissions</b></li></ul></div>
<p class="purpose">To enforce the domain of properties: for instance, that a door can be open or closed but that an animal cannot, or that a person can have a carrying capacity but that a door cannot.</p>
<ul class="toc"><li><a href="16-pp.html#SP7">&#167;7. Searching for permission</a></li><li><a href="16-pp.html#SP8">&#167;8. Granting permission</a></li><li><a href="16-pp.html#SP9">&#167;9. Miscellaneous</a></li></ul><hr class="tocbar">
<p class="commentary firstcommentary"><a id="SP1" class="paragraph-anchor"></a><b>&#167;1. </b>Properties are pieces of data attached to their "owners", but they also
have a common identity wherever they turn up. For example, the property
"carrying capacity" is owned by any person and also by any container, but
it has a common meaning in each case, and in each case it's a number.
</p>
<p class="commentary">Only values can own properties at run-time, but kinds can own properties
during compilation. Thus the Standard Rules declare that the kinds "person"
and "container" have a number called "carrying capacity", and we record
that as a single property which has two owners, both kinds. In the final
story file as compiled, each individual person and container then inherits
the property.
</p>
<p class="commentary">So "value" is not quite the correct concept for "something which owns a
property" &mdash; not only does that fail to allow for kinds, it also puts in
too much; the number 176 is a value, but cannot own properties. Similarly,
"specification" is far too broad a category. But "inference-subject" is
a natural choice, because actual and potential property ownership are
so closely tied together.
</p>
<p class="commentary firstcommentary"><a id="SP2" class="paragraph-anchor"></a><b>&#167;2. </b>Each inference-subject (or INFS) has a list of "property permissions",
each of which gives it permission to own a given property. Each INFS can
also inherit from a more general INFS, and it gets those permissions
automatically. So every individual door has permission to have the "open"
property automatically provided that the "door" kind's INFS has such a
permission. (This prevents our memory from filling up with unnecessary
permissions.)
</p>
<p class="commentary">In addition, it's efficient for each property also to have a list of the
permissions granted for it &mdash; in effect, a "who owns me" list.
</p>
<p class="commentary">That means that whenever a new property permission is created, it must be
entered into two lists &mdash; one for the property, one for the owner.
Fortunately, permissions are never revoked.
</p>
<p class="commentary">To return to the previous example, the "carrying capacity" property would
have a list of two permissions, \(P_1\) and \(P_2\). \(P_1\) would also be found
in the list of permission for the INFS representing the kind "person",
and \(P_2\) in the corresponding list for "container".
</p>
<p class="commentary">This doubled indexing is a tacit form of multiple-inheritance, even though
Inform 7 is officially a single-inheritance language from an objects-and-classes
point of view: "person" is not a kind of "container", nor vice versa,
but both effectively inherit the same behaviour to do with carrying capacity.
</p>
<p class="commentary firstcommentary"><a id="SP3" class="paragraph-anchor"></a><b>&#167;3. </b>Complicating matters, plugins have the ability to attach data of their
own to a permission. For instance, the "parsing" plugin attaches the idea
of a property being visible &mdash; we might say that every thing has an
interior colour, but that it is invisible in the case of a dog and visible
in the case of a broken jar. Because of this, we need to make it possible
for the same property to have multiple permissions in the inheritance
hierarchy above a single point: the jar has a permission for "interior
colour" of its own, even though it inherits this permission from "thing"
in any case.
</p>
<p class="commentary firstcommentary"><a id="SP4" class="paragraph-anchor"></a><b>&#167;4. </b>Anyway, here is a property permission:
</p>
<pre class="displayed-code all-displayed-code code-font">
<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">property_permission</span><span class="plain-syntax"> {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="identifier-syntax">property_owner</span><span class="plain-syntax">; </span><span class="comment-syntax"> to whom permission is granted</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">next_for_this_owner</span><span class="plain-syntax">; </span><span class="comment-syntax"> in list of permissions</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">property_granted</span><span class="plain-syntax">; </span><span class="comment-syntax"> which property is permitted</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">next_for_this_property</span><span class="plain-syntax">; </span><span class="comment-syntax"> in list of permissions</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="identifier-syntax">parse_node</span><span class="plain-syntax"> *</span><span class="identifier-syntax">where_granted</span><span class="plain-syntax">; </span><span class="comment-syntax"> sentence granting the permission</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">struct</span><span class="plain-syntax"> </span><span class="identifier-syntax">general_pointer</span><span class="plain-syntax"> </span><span class="identifier-syntax">pp_storage_data</span><span class="plain-syntax">; </span><span class="comment-syntax"> how we'll compile this at run-time</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">void</span><span class="plain-syntax"> *</span><span class="identifier-syntax">plugin_pp</span><span class="plain-syntax">[</span><span class="constant-syntax">MAX_PLUGINS</span><span class="plain-syntax">]; </span><span class="comment-syntax"> storage for plugins to attach, if they want to</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">CLASS_DEFINITION</span>
<span class="plain-syntax">} </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>The structure property_permission is accessed in 15/pr and here.</li></ul>
<p class="commentary firstcommentary"><a id="SP5" class="paragraph-anchor"></a><b>&#167;5. </b>These macros simply provide access to plugin data, exactly as for world
objects.
</p>
<pre class="definitions code-font"><span class="definition-keyword">define</span> <span class="identifier-syntax">PLUGIN_PP</span><span class="plain-syntax">(</span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">pp</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> ((</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_pp_data</span><span class="plain-syntax"> *) </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">plugin_pp</span><span class="plain-syntax">[</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_plugin</span><span class="plain-syntax">-&gt;</span><span class="identifier-syntax">allocation_id</span><span class="plain-syntax">])</span>
<span class="definition-keyword">define</span> <span class="identifier-syntax">CREATE_PLUGIN_PP_DATA</span><span class="plain-syntax">(</span><span class="identifier-syntax">id</span><span class="plain-syntax">, </span><span class="identifier-syntax">pp</span><span class="plain-syntax">, </span><span class="identifier-syntax">creator</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> (</span><span class="identifier-syntax">pp</span><span class="plain-syntax">)-&gt;</span><span class="identifier-syntax">plugin_pp</span><span class="plain-syntax">[</span><span class="identifier-syntax">id</span><span class="plain-syntax">##</span><span class="identifier-syntax">_plugin</span><span class="plain-syntax">-&gt;</span><span class="identifier-syntax">allocation_id</span><span class="plain-syntax">] = (</span><span class="reserved-syntax">void</span><span class="plain-syntax"> *) (</span><span class="identifier-syntax">creator</span><span class="plain-syntax">(</span><span class="identifier-syntax">pp</span><span class="plain-syntax">));</span>
</pre>
<p class="commentary firstcommentary"><a id="SP6" class="paragraph-anchor"></a><b>&#167;6. </b>This loop trawls through the two cross-lists:
</p>
<pre class="definitions code-font"><span class="definition-keyword">define</span> <span class="identifier-syntax">LOOP_OVER_PERMISSIONS_FOR_PROPERTY</span><span class="plain-syntax">(</span><span class="identifier-syntax">pp</span><span class="plain-syntax">, </span><span class="identifier-syntax">prn</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><a href="15-pr.html#SP13" class="function-link"><span class="function-syntax">Properties::permission_list</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">prn</span><span class="plain-syntax">); </span><span class="identifier-syntax">pp</span><span class="plain-syntax">; </span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_property</span><span class="plain-syntax">)</span>
<span class="definition-keyword">define</span> <span class="identifier-syntax">LOOP_OVER_PERMISSIONS_FOR_INFS</span><span class="plain-syntax">(</span><span class="identifier-syntax">pp</span><span class="plain-syntax">, </span><span class="identifier-syntax">infs</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = *(</span><a href="16-is.html#SP15" class="function-link"><span class="function-syntax">InferenceSubjects::get_permissions</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">infs</span><span class="plain-syntax">)); </span><span class="identifier-syntax">pp</span><span class="plain-syntax">; </span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_owner</span><span class="plain-syntax">)</span>
</pre>
<p class="commentary firstcommentary"><a id="SP7" class="paragraph-anchor"></a><b>&#167;7. Searching for permission. </b>Note that an either/or property and its antonym (say, "open" and "closed")
are equivalent here: to find one is to find the other.
</p>
<p class="commentary">If these were long lists, or searched often, it would be faster to move each
found permission to the front, thus tending to move frequently-sought properties
to the start. But profiling shows that this would save no significant time,
whereas the unpredictable order might make the Index or SHOWME output harder
to verify with <span class="extract"><span class="extract-syntax">intest</span></span>.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="function-syntax">World::Permissions::find</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">World::Permissions::find</span></span>:<br/><a href="16-pp.html#SP8">&#167;8</a><br/>Implications - <a href="5-imp.html#SP6_1_1">&#167;6.1.1</a><br/>Dash - <a href="14-ds2.html#SP10_9_1_1_5_1_3">&#167;10.9.1.1.5.1.3</a>, <a href="14-ds2.html#SP10_9_1_2_3">&#167;10.9.1.2.3</a><br/>Indefinite Appearance - <a href="15-ia.html#SP2">&#167;2</a><br/>The Provision Relation - <a href="15-tpr.html#SP6_2">&#167;6.2</a><br/>Inferences - <a href="16-in.html#SP15">&#167;15</a>, <a href="16-in.html#SP16">&#167;16</a><br/>Complete Model World - <a href="16-cmw.html#SP1_2_1">&#167;1.2.1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="identifier-syntax">infs</span><span class="plain-syntax">,</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</span><span class="plain-syntax">, </span><span class="reserved-syntax">int</span><span class="plain-syntax"> </span><span class="identifier-syntax">allow_inheritance</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prnbar</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">if</span><span class="plain-syntax"> (</span><a href="15-pr.html#SP15" class="function-link"><span class="function-syntax">Properties::is_either_or</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">prn</span><span class="plain-syntax">)) </span><span class="identifier-syntax">prnbar</span><span class="plain-syntax"> = </span><a href="15-ep.html#SP6" class="function-link"><span class="function-syntax">Properties::EitherOr::get_negation</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">prn</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">prn</span><span class="plain-syntax">)</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">while</span><span class="plain-syntax"> (</span><span class="identifier-syntax">infs</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_PERMISSIONS_FOR_INFS</span><span class="plain-syntax">(</span><span class="identifier-syntax">pp</span><span class="plain-syntax">, </span><span class="identifier-syntax">infs</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">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_granted</span><span class="plain-syntax"> == </span><span class="identifier-syntax">prn</span><span class="plain-syntax">) || (</span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_granted</span><span class="plain-syntax"> == </span><span class="identifier-syntax">prnbar</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">pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">infs</span><span class="plain-syntax"> = (</span><span class="identifier-syntax">allow_inheritance</span><span class="plain-syntax">)?(</span><a href="16-is.html#SP13" class="function-link"><span class="function-syntax">InferenceSubjects::narrowest_broader_subject</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">infs</span><span class="plain-syntax">)):</span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</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">NULL</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP8" class="paragraph-anchor"></a><b>&#167;8. Granting permission. </b>This does nothing if permission already exists, simply returning the existing
permission structure; but note the use of <span class="extract"><span class="extract-syntax">allow_inheritance</span></span>. If this is
set to <span class="extract"><span class="extract-syntax">FALSE</span></span>, and we call for the "carrying capacity" property of the
player (say), then we may create a new permission even though the player's
kind ("person") already has one. This is intentional &mdash; it makes it possible
for a property to have different characteristics (say, visibility in the
parser) for some of its owners as compared with others.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="function-syntax">World::Permissions::grant</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">World::Permissions::grant</span></span>:<br/>Properties - <a href="15-pr.html#SP4_6">&#167;4.6</a><br/>The Provision Relation - <a href="15-tpr.html#SP5">&#167;5</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="identifier-syntax">infs</span><span class="plain-syntax">, </span><span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</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">allow_inheritance</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">new_pp</span><span class="plain-syntax"> = </span><a href="16-pp.html#SP7" class="function-link"><span class="function-syntax">World::Permissions::find</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">infs</span><span class="plain-syntax">, </span><span class="identifier-syntax">prn</span><span class="plain-syntax">, </span><span class="identifier-syntax">allow_inheritance</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">new_pp</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</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">PROPERTY_PROVISION</span><span class="plain-syntax">, </span><span class="string-syntax">"Allowing $j to provide $Y\n"</span><span class="plain-syntax">, </span><span class="identifier-syntax">infs</span><span class="plain-syntax">, </span><span class="identifier-syntax">prn</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="16-pp.html#SP8_1" class="named-paragraph-link"><span class="named-paragraph">Create the new permission structure</span><span class="named-paragraph-number">8.1</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="16-pp.html#SP8_2" class="named-paragraph-link"><span class="named-paragraph">Add the new permission to the owner's list</span><span class="named-paragraph-number">8.2</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="16-pp.html#SP8_3" class="named-paragraph-link"><span class="named-paragraph">Add the new permission to the property's list</span><span class="named-paragraph-number">8.3</span></a></span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="named-paragraph-container code-font"><a href="16-pp.html#SP8_4" class="named-paragraph-link"><span class="named-paragraph">Notify plugins that a new permission has been issued</span><span class="named-paragraph-number">8.4</span></a></span><span class="plain-syntax">;</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">new_pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP8_1" class="paragraph-anchor"></a><b>&#167;8.1. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Create the new permission structure</span><span class="named-paragraph-number">8.1</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax"> = </span><span class="identifier-syntax">CREATE</span><span class="plain-syntax">(</span><span class="reserved-syntax">property_permission</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">where_granted</span><span class="plain-syntax"> = </span><span class="identifier-syntax">current_sentence</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">pp_storage_data</span><span class="plain-syntax"> = </span><a href="16-is.html#SP24" class="function-link"><span class="function-syntax">InferenceSubjects::new_permission_granted</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">infs</span><span class="plain-syntax">);</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="16-pp.html#SP8">&#167;8</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP8_2" class="paragraph-anchor"></a><b>&#167;8.2. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Add the new permission to the owner's list</span><span class="named-paragraph-number">8.2</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_owner</span><span class="plain-syntax"> = </span><span class="identifier-syntax">infs</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> **</span><span class="identifier-syntax">ppl</span><span class="plain-syntax"> = </span><a href="16-is.html#SP15" class="function-link"><span class="function-syntax">InferenceSubjects::get_permissions</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">infs</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">ppl</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) *</span><span class="identifier-syntax">ppl</span><span class="plain-syntax"> = </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = *</span><span class="identifier-syntax">ppl</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">while</span><span class="plain-syntax"> (</span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_owner</span><span class="plain-syntax">) </span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_owner</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_owner</span><span class="plain-syntax"> = </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_owner</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="16-pp.html#SP8">&#167;8</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP8_3" class="paragraph-anchor"></a><b>&#167;8.3. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Add the new permission to the property's list</span><span class="named-paragraph-number">8.3</span></span><span class="comment-syntax"> =</span>
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_granted</span><span class="plain-syntax"> = </span><span class="identifier-syntax">prn</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><a href="15-pr.html#SP13" class="function-link"><span class="function-syntax">Properties::permission_list</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">prn</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">pp</span><span class="plain-syntax"> == </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><a href="15-pr.html#SP13" class="function-link"><span class="function-syntax">Properties::set_permission_list</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">prn</span><span class="plain-syntax">, </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> } </span><span class="reserved-syntax">else</span><span class="plain-syntax"> {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">while</span><span class="plain-syntax"> (</span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_property</span><span class="plain-syntax"> != </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">) </span><span class="identifier-syntax">pp</span><span class="plain-syntax"> = </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_property</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_property</span><span class="plain-syntax"> = </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">next_for_this_property</span><span class="plain-syntax"> = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="16-pp.html#SP8">&#167;8</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP8_4" class="paragraph-anchor"></a><b>&#167;8.4. </b><span class="named-paragraph-container code-font"><span class="named-paragraph-defn">Notify plugins that a new permission has been issued</span><span class="named-paragraph-number">8.4</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">int</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">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">i</span><span class="plain-syntax">=0; </span><span class="identifier-syntax">i</span><span class="plain-syntax">&lt;</span><span class="constant-syntax">MAX_PLUGINS</span><span class="plain-syntax">; </span><span class="identifier-syntax">i</span><span class="plain-syntax">++) </span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">plugin_pp</span><span class="plain-syntax">[</span><span class="identifier-syntax">i</span><span class="plain-syntax">] = </span><span class="identifier-syntax">NULL</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><a href="26-pc.html#SP7" class="function-link"><span class="function-syntax">Plugins::Call::new_permission_notify</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">new_pp</span><span class="plain-syntax">);</span>
</pre>
<ul class="endnotetexts"><li>This code is used in <a href="16-pp.html#SP8">&#167;8</a>.</li></ul>
<p class="commentary firstcommentary"><a id="SP9" class="paragraph-anchor"></a><b>&#167;9. Miscellaneous. </b>With the two fundamental operations out of the way, there's not much left
to do except provide access to the details of the permission.
</p>
<pre class="displayed-code all-displayed-code code-font">
<span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="function-syntax">World::Permissions::get_property</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">World::Permissions::get_property</span></span>:<br/>Properties of Values - <a href="15-pov.html#SP4">&#167;4</a><br/>Emit Property Values - <a href="15-epv.html#SP1_1_4">&#167;1.1.4</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</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">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_granted</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
<span class="reserved-syntax">inference_subject</span><span class="plain-syntax"> *</span><span class="function-syntax">World::Permissions::get_subject</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">World::Permissions::get_subject</span></span>:<br/><a href="16-pp.html#SP10">&#167;10</a><br/>Instances - <a href="6-ins.html#SP10">&#167;10</a><br/>Emit Property Values - <a href="15-epv.html#SP3_1">&#167;3.1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</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">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">property_owner</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
<span class="identifier-syntax">general_pointer</span><span class="plain-syntax"> </span><span class="function-syntax">World::Permissions::get_storage_data</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">World::Permissions::get_storage_data</span></span>:<br/>Properties of Values - <a href="15-pov.html#SP3">&#167;3</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</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">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">pp_storage_data</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
<span class="identifier-syntax">parse_node</span><span class="plain-syntax"> *</span><span class="function-syntax">World::Permissions::where_granted</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">World::Permissions::where_granted</span></span>:<br/>Properties of Values - <a href="15-pov.html#SP4_1">&#167;4.1</a></span></button><span class="plain-syntax">(</span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</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">pp</span><span class="plain-syntax">-&gt;</span><span class="element-syntax">where_granted</span><span class="plain-syntax">;</span>
<span class="plain-syntax">}</span>
</pre>
<p class="commentary firstcommentary"><a id="SP10" class="paragraph-anchor"></a><b>&#167;10. </b>A case where it's convenient to run through permissions for a given
property &mdash; when indexing who can own it.
</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">World::Permissions::index</span><button class="popup" onclick="togglePopup('usagePopup7')"><span class="comment-syntax">?</span><span class="popuptext" id="usagePopup7">Usage of <span class="code-font"><span class="function-syntax">World::Permissions::index</span></span>:<br/>Instances - <a href="6-ins.html#SP36">&#167;36</a><br/>Either-Or Properties - <a href="15-ep.html#SP17">&#167;17</a></span></button><span class="plain-syntax">(</span><span class="identifier-syntax">OUTPUT_STREAM</span><span class="plain-syntax">, </span><span class="reserved-syntax">property</span><span class="plain-syntax"> *</span><span class="identifier-syntax">prn</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">ac</span><span class="plain-syntax"> = </span><span class="constant-syntax">0</span><span class="plain-syntax">, </span><span class="identifier-syntax">s</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">for</span><span class="plain-syntax"> (</span><span class="identifier-syntax">s</span><span class="plain-syntax"> = </span><span class="constant-syntax">1</span><span class="plain-syntax">; </span><span class="identifier-syntax">s</span><span class="plain-syntax"> &lt;= </span><span class="constant-syntax">2</span><span class="plain-syntax">; </span><span class="identifier-syntax">s</span><span class="plain-syntax">++) {</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">property_permission</span><span class="plain-syntax"> *</span><span class="identifier-syntax">pp</span><span class="plain-syntax">;</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">LOOP_OVER_PERMISSIONS_FOR_PROPERTY</span><span class="plain-syntax">(</span><span class="identifier-syntax">pp</span><span class="plain-syntax">, </span><span class="identifier-syntax">prn</span><span class="plain-syntax">) {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">wording</span><span class="plain-syntax"> </span><span class="identifier-syntax">W</span><span class="plain-syntax"> = </span><a href="16-is.html#SP23" class="function-link"><span class="function-syntax">InferenceSubjects::get_name_text</span></a><span class="plain-syntax">(</span><a href="16-pp.html#SP9" class="function-link"><span class="function-syntax">World::Permissions::get_subject</span></a><span class="plain-syntax">(</span><span class="identifier-syntax">pp</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">Wordings::nonempty</span><span class="plain-syntax">(</span><span class="identifier-syntax">W</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">s</span><span class="plain-syntax"> == </span><span class="constant-syntax">1</span><span class="plain-syntax">) </span><span class="identifier-syntax">ac</span><span class="plain-syntax">++;</span>
<span class="plain-syntax"> </span><span class="reserved-syntax">else</span><span class="plain-syntax"> {</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">WRITE</span><span class="plain-syntax">(</span><span class="string-syntax">"&lt;/i&gt;%+W&lt;i&gt;"</span><span class="plain-syntax">, </span><span class="identifier-syntax">W</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> </span><span class="identifier-syntax">ac</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">ac</span><span class="plain-syntax"> == </span><span class="constant-syntax">1</span><span class="plain-syntax">) </span><span class="identifier-syntax">WRITE</span><span class="plain-syntax">(</span><span class="string-syntax">" or "</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">ac</span><span class="plain-syntax"> &gt; </span><span class="constant-syntax">1</span><span class="plain-syntax">) </span><span class="identifier-syntax">WRITE</span><span class="plain-syntax">(</span><span class="string-syntax">", "</span><span class="plain-syntax">);</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax"> }</span>
<span class="plain-syntax">}</span>
</pre>
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