Editing QuakeC Simple Types

<H1><FONT COLOR="#007F00">2. The Quake-C Basic Types</FONT></H1>


<h2>2.1 The simple Types</h2>

<h4>2.1.1 Void type</h4>

<p>An empty result, mostly used for definition of procedures (i.e. functions 
that return no result at all).
</p>

<h4>2.1.2 Float type</h4>

<p>A floating point value.</p>
<p>Floats are also used to store booleans (TRUE, FALSE) or integer values
link counters, or bit flags.
<pre>
    Valid syntax: 12  1.6  0.5  -100
  
    Invalid syntax: .5  -.50  .690
</pre>
</p>
<p>A parsing ambiguity is present with negative constants. "a-5" will be parsed 
as "a", then "-5", causing an error.  Separate the - from the digits with a 
space "a - 5" to get the proper behavior.
</p>

<h4>2.1.3 Vector type</h4>

<p>A vector, made of 3 <a href="qc-types.htm#float" target="content">float</a> coordinates.
<br>
Used to represent positions or directions in 3D space.

<br>
Valid syntax: <b>'0 0 0'</b>  or <b>'20.5 -10 0.00001'</b>
<br>
</p>
<p>Note the simple quotes around the vector. Do not use
double quotes, they are reserved for strings.</p>

<p>If you declare a vector <b>foobar</b>, then you can
access it's x, y and z fields with: <b>foobar_x</b>,

<b>foobar_y</b>,<b>foobar_z</b>.
</p>

<h4>2.1.4 String type</h4>

<p>This is used to store character string.
<br>
Used to indicate file names, or messages to be broadcast to players.
<br>
Valid syntax: <b>"maps/jrwiz1.bsp"</b> or <b>"ouch!\
"</b>

<br>
Use <b>\
</b> for newline.
</p>
<p>Note: that character strings cannot be modified, or concatenated.
Because they are stored at fixed locations in memory, and if
would be postentially troublesome to allow modification.
</p>

<h4>2.1.5 entity type</h4>

<p>The reference of an entity in the game, like things, players, monsters.<br>

For instance, this is the type of the entities self
and other.
</p> 
<p>The entity type is a structured type, made of [[fields]].<br>
A description of each field is available.
</p>

 
<hr>
<h2>2.2 The field types</h2>

<h4>2.2.1 What's a field?</h4>

<p>Countrary to the other types, the [[entity]] type 
is a reference to an instance of a structured object, that contains
many informations of totally different kinds.</p>

<p>To access all these informations conveniently, they are stored as
fields of the entity object, and each field is given a name and a type,
that makes it distinct of the others.</p>

<p>Some of the fields do not store value, but instead they store the
function to be executed in certain conditions. They are called the
<b>methods</b> that can be aplied to the object.</p>

<p>If Quake-C was an object oriented programming language, those method
functions and would be distinguished from the other fields. And, above
all, you would be able to create new object types, with their own fields.</p>

<p>As Quake-C stands currently, <b>all the field definitions</b> are
definitions of entity fields. So anywhere in your code you could add
definition of new fields, and the compiler would interpret them
as an extension of the entity definition.</p>


<h4>2.2.2 Creating new fields</h4>

<p>The only way to extend the <a href="qc-types.htm#entity" target="content">entity</a> type
is to add some fields at the end of the structures.</p>

<p>This is done via a field definitions, whose general structure is:
<pre>
   <b>.<a href="qc-types.htm#QC-TSMP" target="content">type</a> field_name;</b>
</pre>
</p>

<p> For instance, if you wanted to add a sling to the game, and needed
to store the count of pellets for every player, you would add
the following line in the source code:
<pre>
   <b>.<a href="qc-types.htm#QC-TSMP" target="content">float</a> ammo_sling;</b>
</pre>
That will add a fields <b>ammo_sling</b> to every entity in the game,
and in particular to the player entities.
</p>

<p>Here are all the possible definitions of entity fields, with their <a href="qc-types.htm#QC-TSMP" target="content">types</a>:
<pre>
    <a name="dot_float">.float</a> <i>field_name</i>;
    <a name="dot_string">.string</a> <i>field_name</i>;
    <a name="dot_vector">.vector</a> <i>field_name</i>;
    <a name="dot_entity">.entity</a> <i>field_name</i>;

</pre>
</p>

<p>The strange bit is that you can add those type definitions almost
anywhere in the source code. They are not supposed to be grouped in
a single place, where the entity type would be defined.
</p>

<h4>2.2.3 Allowed modifications of types</h4>

<p>In the first file read by the Quake-C compiler, <b>[[defs.qc]]</b>,
there must be a definition for the entity fields, and world fields.
This definition is hard coded. You had better not touch it,
or you will have to recompile Quake itself.
<p>

<p>The globals are defined before the special definition
<b>[[void end_sys_globals;]]</b><br>

The entity fields are defined before the special
definition <b>[[void end_sys_fields;]]</b></p>

<p>It's not important if you don't understand the nonsense
above. It's an ugly hack. Just <b>don't modify defs.qc</b> 
before those two tags, and you won't be in trouble.</p>
<hr>