Object Oriented Programming in Script/Objects - Revision history

Andrew Branscom: /* Introduction */

2026-01-02T18:16:53Z

Introduction

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	Any unknown symbol encountered in a compilation is assumed to be the ID of some object which is to be defined later in the source file. If no object with the symbol as its name is encountered by the end of the file, an error will be raised.		Any unknown symbol encountered in a compilation is assumed to be the ID of some object which is to be defined later in the source file. If no object with the symbol as its name is encountered by the end of the file, an error will be raised.
	<blockquote>		</blockquote>

	==<br /> References ==		==<br /> References ==

Andrew Branscom at 18:16, 2 January 2026

2026-01-02T18:16:25Z

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			[[Category:SCI Pages]]
	[[Official SCI Documentation]]<br />		[[Official SCI Documentation]]<br />
			[[Object Oriented Programming in Script\|Table of Contents]]

	<div align="center">		<div align="center">
	Chapter:		Chapter:
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	[[Object Oriented Programming in Script/An Extended Example\|6]] \|		[[Object Oriented Programming in Script/An Extended Example\|6]] \|
	[[Object Oriented Programming in Script/Index\|Index]]		[[Object Oriented Programming in Script/Index\|Index]]
	</div><br />		</div>
			<div align="center"><span style="font-size: 22pt">Objects</span><br />''Author: [[Jeff Stephenson]]''<br />''1988-04-04''</div></div>

	~~<div align="center"><span style="font-size: 22pt">Objects</span>~~<br />		<br />
	~~''Author: [[Jeff Stephenson]]''~~<br />		==<br /> Introduction ==
	~~''Date: 4 April 1988''</div>~~

	~~ ~~

			<blockquote>
	Objects are specific instances of a class, and are defined using the instance statement:		Objects are specific instances of a class, and are defined using the instance statement:

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	Any unknown symbol encountered in a compilation is assumed to be the ID of some object which is to be defined later in the source file. If no object with the symbol as its name is encountered by the end of the file, an error will be raised.		Any unknown symbol encountered in a compilation is assumed to be the ID of some object which is to be defined later in the source file. If no object with the symbol as its name is encountered by the end of the file, an error will be raised.
			<blockquote>

	~~ ~~		==<br /> References ==

			<references /><!-- Do not edit this section. It is autopopulated by <ref></ref> tags -->

	~~;Notes~~		==<br /> Also See ==
	<~~references~~ />

			* [[:Category:SCI Documentation\|SCI Documentation]]
			* [[:Category:Official SCI Documentation\|Official SCI Documentation]]
			* [[:Category:SCI Scripting]]
			* [[:Category:Objects\|Objects]]


	[[Object Oriented Programming in Script \| Table of Contents]]		[[Official SCI Documentation]]<br />
			[[Object Oriented Programming in Script\|Table of Contents]]
	~~ ~~

	<span style="float: left">[[Object Oriented Programming in Script/Classes\|< Previous: Classes]]</span>		<span style="float: left">[[Object Oriented Programming in Script/Classes\|< Previous: Classes]]</span>
	<span style="float: right">[[Object Oriented Programming in Script/Sending Messages\|Next: Sending Messages >]]</span>		<span style="float: right">[[Object Oriented Programming in Script/Sending Messages\|Next: Sending Messages >]]</span>


			[[Category:References]]
			[[Category:SCI References]]
			[[Category:Historical Pages]]
			[[Category:SCI Historical Pages]]
			[[Category:Development]]
			[[Category:SCI Development]]
	[[Category:Documentation]]		[[Category:Documentation]]
	[[Category:SCI Documentation]]		[[Category:SCI Documentation]]
			[[Category:Official Documentation]]
			[[Category:Official SCI Documentation]]
	[[Category:Scripting]]		[[Category:Scripting]]
	[[Category:SCI Scripting]]		[[Category:SCI Scripting]]
	[[Category:SCI Objects]]		[[Category:SCI Objects]]

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sierraw>Andrew Branscom at 03:48, 3 March 2018

2018-03-03T03:48:12Z

New page

[[Official SCI Documentation]]<br />

<div align="center">
Chapter:
[[Object Oriented Programming in Script/Object Oriented Programming|1]] |
[[Object Oriented Programming in Script/Object Oriented Terminology|2]] |
[[Object Oriented Programming in Script/Classes|3]] |
[[Object Oriented Programming in Script/Objects|4]] |
[[Object Oriented Programming in Script/Sending Messages|5]] |
[[Object Oriented Programming in Script/An Extended Example|6]] |
[[Object Oriented Programming in Script/Index|Index]]
</div><br />

<div align="center"><span style="font-size: 22pt">Objects</span><br />
''Author: [[Jeff Stephenson]]''<br />
''Date: 4 April 1988''</div>

 

Objects are specific instances of a class, and are defined using the instance statement:

<blockquote>
<div class="CodeBlockHeader">Code:</div>
<syntaxhighlight lang="sci">
(instance anObject of aClass
(properties
aProperty: value
...
)

(method (aMethod [p1 p2 ...] [&tmp t1 t2 ...])
code
)
...

[(procedure ...)]
)</syntaxhighlight>
</blockquote>

This defines an Object as an instance of class aClass. The properties and method statements are optional and are used to over-ride the default values and methods inherited from aClass.

The ID of an object or a class is what tells the sci kernel where to send messages. The object ID is obtained by simply writing the object's name wherever an expression is valid -- it can be assigned to a variable or passed as a parameter to a procedure. Thus, if we define egoObj as an instance of class Ego,

<blockquote>
<div class="CodeBlockHeader">Code:</div>
<syntaxhighlight lang="sci">
(instance egoObj of Ego)
</syntaxhighlight>
</blockquote>

we can assign the ID of egoObj to the global variable ego:

<blockquote>
<div class="CodeBlockHeader">Code:</div>
<syntaxhighlight lang="sci">
(global ego 0)
(= ego egoObj)
</syntaxhighlight>
</blockquote>

Once this has been done, the following two expressions are equivalent:

<blockquote>
<div class="CodeBlockHeader">Code:</div>
<syntaxhighlight lang="sci">
(ego x?)
(egoObj x?)
</syntaxhighlight>
</blockquote>

To find the distance from the object ego to the object wolf, we can pass the wolf's ID as an argument to ego's distanceTo: method:

<blockquote>
<div class="CodeBlockHeader">Code:</div>
<syntaxhighlight lang="sci">
(ego distanceTo: wolf)
</syntaxhighlight>
</blockquote>

Any unknown symbol encountered in a compilation is assumed to be the ID of some object which is to be defined later in the source file. If no object with the symbol as its name is encountered by the end of the file, an error will be raised.

 

;Notes
<references />

 

[[Object Oriented Programming in Script | Table of Contents]]

 

<span style="float: left">[[Object Oriented Programming in Script/Classes|< Previous: Classes]]</span>
<span style="float: right">[[Object Oriented Programming in Script/Sending Messages|Next: Sending Messages >]]</span>

 

[[Category:Documentation]]
[[Category:SCI Documentation]]
[[Category:Scripting]]
[[Category:SCI Scripting]]
[[Category:SCI Objects]]