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The <code>elements</code> API contains methods and constants for creating and modifying elements.

'''The shorter alias <code>elem</code> is also available.'''

Unless stated otherwise, all functions raise errors if supplied with parameters that disagree with their descriptions.

== Methods ==

=== elements.allocate ===

Create a new element.

<pre>elemNumber = elements.allocate(group, iname)</pre>
* <code>group</code>: string without underscores (<code>_</code>), the group the element belongs to; gets uppercased by the function
* <code>iname</code>: string without underscores (<code>_</code>), the internal name of the element; gets uppercased by the function
* <code>elemNumber</code>: the positive element number allocated for the element created, or <code>-1</code> on error, if there are no free element numbers left

<code>group</code> should be something unique to your script, and should be the same across the entire script. It is common to use a simpler version of your username or the script’s name, for example if your script is called ''Ultimate Chemistry Pack v3'', you might use <code>&quot;CHEMPACK3&quot;</code> as the group name.

<code>iname</code> should be unique to the element within your script, and should ultimately resemble the [[#elements.property|<code>Name</code> property]] of the element. For example, if your element’s name is ''C-6'' you should use <code>C6</code> as the internal name.

The resulting element identifier must be unique across all scripts in use at any point in time. Elements that seem like built-in elements, i.e. ones in the group <code>DEFAULT</code>, cannot be created. Note that, as stated above, both <code>group</code> and <code>iname</code> get uppercased, so <code>elements.allocate(&quot;CheMpaCk3&quot;, &quot;c6&quot;)</code> is equivalent to <code>elements.allocate(&quot;CHEMPACK3&quot;, &quot;C6&quot;)</code>.

Make the choice such that it is convenient to refer to your element via an [[#elements.group_pt_iname|<code>elements.[group]_PT_[iname]</code> constant]]. While it is perfectly possible to type <code>elem[&quot;Ultimate Chemistry Pack v3_PT_C-6&quot;]</code>, it is much more convenient to type <code>elem.CHEMPACK3_PT_C6</code>.

The new element is created with all the default properties, and will not be visible until you modify it to show up in the menu.

=== elements.property ===

Query or update a property of an element.

<pre>propValue = elements.property(elemNumber, propName) -- query variant
elements.property(elemNumber, propName, propValue) -- update variant
elements.property(elemNumber, &quot;Update&quot;, propValue, [runWhen]) -- special update variant for the Update property</pre>
* <code>elemNumber</code>: number of the element whose property is to be queried or updated
* <code>propName</code>: string, name of the property to be queried or updated
* <code>propValue</code>: various types, value of the property to be queried or updated
* <code>runWhen</code>: number, specifies when the update function should be run, one of:
** <code>elements.UPDATE_AFTER</code>: run before the built-in update function, this is the default
** <code>elements.UPDATE_REPLACE</code>: run instead of the built-in update function
** <code>elements.UPDATE_BEFORE</code>: run after the built-in update function

For more information on what properties there are to use in elements.property, and how to use them, see this page: [[Element_Properties]].

When working with the "MenuSection" or the "Properties" property, use one of the provided [[#Constants|constants]].

The "Identifier" property is read-only and cannot be set.

Several event callback functions are implemented, such as "Update" and "Graphics". To set these, use a function for <code>propValue</code>. They are not included in the tables created with elements.element, and the functions can't be returned with elements.property either. This means copying all of an elements properties using elements.element will not set event callbacks for the new element. For help on creating these, see [[Element_Properties#Callback_functions]].

=== elements.element ===

Query all or update multiple properties of an element.

<pre>elemProps = elements.element(elemNumber) -- query variant
elements.element(elemNumber, elemProps) -- update variant</pre>
* <code>elemNumber</code>: number of the element whose properties are to be queried or update
* <code>elemProps</code>: table that maps property names to property values

The keys and values of <code>elemProps</code> are the same as the <code>propName</code> and <code>propValue</code> parameters of [[#elements.property|elements.property]]. The query variant returns all properties of the element in <code>elemProps</code> with the same caveats as [[#elements.property|elements.property]]. The update variant accepts any subset of properties, only updates the ones present in the table, applying the same checks as [[#elements.property|elements.property]].

This function is commonly used to base an element off another element by first copying all properties of the source element and applying them to the new element, and then customizing the new element a bit afterwards:

<pre>local purpleGold = elem.allocate(&quot;EXAMPLE&quot;, &quot;PGLD&quot;)
assert(purpleGold ~= -1, &quot;ran out of element numbers&quot;)
elem.element(purpleGold, elem.element(elem.DEFAULT_PT_GOLD))
elem.property(purpleGold, &quot;Name&quot;, &quot;PGLD&quot;)
elem.property(purpleGold, &quot;Color&quot;, 0x8040FF)</pre>

=== elements.exists ===

Check whether a number is a real element number and refers to an element.

<pre>exists = elements.exists(elemNumber)</pre>
* <code>elemNumber</code>: number of the element to be checked
* <code>exists</code>: boolean, <code>true</code> if <code>elemNumber</code> refers to an element

If an element exists, there exists a corresponding [[#elements.group_pt_iname|<code>elements.[group]_PT_[iname]</code> constant]], and conversely, if there exists such a constant, there exists a corresponding element.

=== elements.free ===

Free a previously allocated element.

<pre>elements.free(elemNumber)</pre>
* <code>elemNumber</code>: number of the element to be freed

The element number is freed and can used later by another script. Built-in elements, i.e. elements in the group <code>DEFAULT</code>, cannot be freed.

<span id="elements.getbyname"></span>
=== elements.getByName ===

Find an element by name, the [[#elements.property|<code>Name</code> property]].

<pre>elementNumber = elements.getByName(name)</pre>
* <code>name</code>: string, the name to find the element by
* <code>elemNumber</code>: positive number of the element <code>name</code> refers to, or <code>-1</code> on error if no such element exists

This function converts a human-friendly element name to an element number, essentially the same way the PROP tool or the console works.

<span id="elements.loaddefault"></span>
=== elements.loadDefault ===

Restore the set of elements to its initial state at startup.

<pre>elements.loadDefault()</pre>
This frees all elements created and resets all properties of all built-in elements to their defaults.

== Constants ==

<span id="elements.group_pt_iname"></span>
=== elements.[group]_PT_[iname] ===

<pre>watrNumber = elements.DEFAULT_PT_WATR</pre>
There are two ways to refer to elements: element numbers and element identifiers, which are strings of the form <code>&quot;[group]_PT_[iname]&quot;</code>. Both <code>[group]</code> and <code>[iname]</code> can be any string without underscores (<code>_</code>). All built-in elements are in group <code>DEFAULT</code>. For example, the identifier of WATR is <code>&quot;DEFAULT_PT_WATR&quot;</code>, because WATR belongs to the group <code>DEFAULT</code> and its internal name is <code>WATR</code>. This is different from the [[#elements.property|<code>Name</code> property]].

These constants map element identifiers to element numbers. The element number of WATR is <code>2</code>, so <code>elements.DEFAULT_PT_WATR</code> is also <code>2</code>.

=== Properties ===

These constants should be used when setting "Properties". More info on the properties can be found here: [[Element_Properties#.Property_Constants]]

; TYPE_PART
; TYPE_LIQUID
; TYPE_GAS
; TYPE_SOLID
; TYPE_ENERGY
; PROP_CONDUCTS
; PROP_BLACK
; PROP_NEUTPENETRATE
; PROP_NEUTABSORB
; PROP_NEUTPASS
; PROP_DEADLY
; PROP_HOT_GLOW
; PROP_LIFE
; PROP_RADIOACTIVE
; PROP_LIFE_DEC
; PROP_LIFE_KILL
; PROP_LIFE_KILL_DEC
; PROP_SPARKSETTLE
; PROP_NOAMBHEAT
; PROP_DRAWONCTYPE 
; PROP_NOCTYPEDRAW 

=== Menu sections ===
These are used for the MenuSection property

; SC_WALL
; SC_ELEC
; SC_POWERED
; SC_SENSOR
; SC_FORCE
; SC_EXPLOSIVE
; SC_GAS
; SC_LIQUID
; SC_POWDERS
; SC_SOLIDS
; SC_NUCLEAR
; SC_SPECIAL
; SC_LIFE
; SC_TOOL
; SC_DECO
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