Structures - Revision history

ELowell: /* Structure blocks and variable declaration */

2016-05-24T16:49:57Z

Structure blocks and variable declaration

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	The behavior of object variables contrasts with this: assignment is by reference, as described later.		The behavior of object variables contrasts with this: assignment is by reference, as described later.
	</blockquote">		</blockquote>

	==Working with structure variables==		==Working with structure variables==

JAL at 18:41, 14 April 2014

2014-04-14T18:41:57Z

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JAL: minor cleanup

2014-04-14T16:29:08Z

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JAL: /* See also */

2013-10-14T22:10:34Z

JALWiccan: Automatically generated page update

2013-10-14T20:05:31Z

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	</ul>		</ul>

	[[Category:~~Janus SOAP ULI~~ topics]]		[[Category:SOUL object-oriented programming topics]]

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	End Structure [structureName]		End Structure [structureName]

	where structureName can consist of any valid alphanumeric and other non-separator characters, and suffix is a set of characters that must end the name of any variable being declared with the structure. The variables in a structure are sometimes referred to as the ~~“structure members”~~.		where structureName can consist of any valid alphanumeric and other non-separator characters, and suffix is a set of characters that must end the name of any variable being declared with the structure. The variables in a structure are sometimes referred to as the “structure members”.

	Note: As of Sirius Mods version 7.3, you can also define ~~“local”~~ structures (~~“Local~~ classes, enumerations, and ~~structures”~~ on page 381) that apply only in the scope in which they are defined, which may be within a class or a method or another level of the program.		Note: As of Sirius Mods version 7.3, you can also define “local” structures (“Local classes, enumerations, and structures” on page 381) that apply only in the scope in which they are defined, which may be within a class or a method or another level of the program.

	The variable declarations consist of one or more declarations of exactly the same format as a <var class="product">User Language</var> %variable declaration, with the exception that the variable names must not begin with a percent sign:		The variable declarations consist of one or more declarations of exactly the same format as a <var class="product">User Language</var> %variable declaration, with the exception that the variable names must not begin with a percent sign:
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	'''Note:''' Structure assignment is assignment by value: the elements of the source structure are copied one by one (very efficiently) to the target structure, so that subsequent changes to the source structure variable do not affect the target.		'''Note:''' Structure assignment is assignment by value: the elements of the source structure are copied one by one (very efficiently) to the target structure, so that subsequent changes to the source structure variable do not affect the target.

	For example, the following code would print ~~“blue”~~,		For example, the following code would print “blue”,

	%sunshine is structure budgie		%sunshine is structure budgie
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	%lot(%x):bid(%y) = %bid		%lot(%x):bid(%y) = %bid

	Structure variables reside in VTBL in space allocated at compile-time so, as stated earlier, have no need to be ~~“prepared”~~. However, at times it may be useful to ~~“prepare”~~ a structure variable, that is, set it to its initial default values. Because there is no ~~“Prepare Structure”~~ statement, this is best accomplished either by setting the individual members or (more efficiently) by keeping a template or initial structure variable to assign to a structure variable which is to be logically ~~“prepared”~~:		Structure variables reside in VTBL in space allocated at compile-time so, as stated earlier, have no need to be “prepared”. However, at times it may be useful to “prepare” a structure variable, that is, set it to its initial default values. Because there is no “Prepare Structure” statement, this is best accomplished either by setting the individual members or (more efficiently) by keeping a template or initial structure variable to assign to a structure variable which is to be logically “prepared”:

	structure budgie		structure budgie
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	end structure		end structure

	All Structure variables of type Budgie would have to end in the characters “.~~parakeet”~~, making it relatively east to detect references to this type of variable in <var class="product">User Language</var> code:		All Structure variables of type Budgie would have to end in the characters “.parakeet”, making it relatively east to detect references to this type of variable in <var class="product">User Language</var> code:
	%my.parakeet:color = 'blue'		%my.parakeet:color = 'blue'
	...		...
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	Some basic guidelines for when a Structure is to be used instead of an object are:		Some basic guidelines for when a Structure is to be used instead of an object are:

	* Any data structure that represents a real entity or object — a noun, if you will — should be an object, not a structure. Structures should generally be used for measurements or attributes of objects.		* Any data structure that represents a real entity or object — a noun, if you will — should be an object, not a structure. Structures should generally be used for measurements or attributes of objects.
	* Despite the richness of the structure facility, structures should be small, that is, with no more than five members and usually only two or three. If they get much bigger than this, it is likely that an object is a more appropriate model for the data being represented.		* Despite the richness of the structure facility, structures should be small, that is, with no more than five members and usually only two or three. If they get much bigger than this, it is likely that an object is a more appropriate model for the data being represented.
	* Any data structure that represents an attribute of an object or method — an adjective, if you will — might make sense as a Structure.		* Any data structure that represents an attribute of an object or method — an adjective, if you will — might make sense as a Structure.
	* Because structures are statically allocated in VTBL, accessing data in a structure can be somewhat more efficient than accessing data in an object (and in an image, incidentally), so might be useful in cases where performance of individual member access is the paramount concern.		* Because structures are statically allocated in VTBL, accessing data in a structure can be somewhat more efficient than accessing data in an object (and in an image, incidentally), so might be useful in cases where performance of individual member access is the paramount concern.

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	<li>[[Object variables]]		<li>[[Object variables]]
	<li>[[Methods]]		<li>[[Methods]]
	<li>[[Janus SOAP essentials]]		<li>[[Janus SOAP ULI essentials]]
	</ul>		</ul>

	[[Category:Janus SOAP ULI topics]]		[[Category:Janus SOAP ULI topics]]

JAL at 16:14, 11 October 2012

2012-10-11T16:14:04Z

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	A '''structure''' is, as the name suggests, a layout of standard User Language variables.		A '''structure''' is, as the name suggests, a layout of standard <var class="product">User Language</var> variables.

	The layout of a structure is described by a Structure block, and variables with that layout are indicated by the Structure datatype on variable declarations.		The layout of a structure is described by a Structure block, and variables with that layout are indicated by the Structure datatype on variable declarations.
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	Note: As of Sirius Mods version 7.3, you can also define “local” structures (“Local classes, enumerations, and structures” on page 381) that apply only in the scope in which they are defined, which may be within a class or a method or another level of the program.		Note: As of Sirius Mods version 7.3, you can also define “local” structures (“Local classes, enumerations, and structures” on page 381) that apply only in the scope in which they are defined, which may be within a class or a method or another level of the program.

	The variable declarations consist of one or more declarations of exactly the same format as a User Language %variable declaration, with the exception that the variable names must not begin with a percent sign:		The variable declarations consist of one or more declarations of exactly the same format as a <var class="product">User Language</var> %variable declaration, with the exception that the variable names must not begin with a percent sign:

	structure budgie		structure budgie
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	end structure		end structure

	Like a standard User Language %variable declaration, the keyword Is is optional. Valid datatypes include String, Float, Fixed, Longstring, and (as described later) Structure, Object, Collection, and Enumeration. Structure members can also be Arrays, but cannot be Static or Global. Structure members may contain an Initial clause that indicates the initial value for a member in an instance of the structure.		Like a standard <var class="product">User Language</var> %variable declaration, the keyword Is is optional. Valid datatypes include String, Float, Fixed, Longstring, and (as described later) Structure, Object, Collection, and Enumeration. Structure members can also be Arrays, but cannot be Static or Global. Structure members may contain an Initial clause that indicates the initial value for a member in an instance of the structure.

	A Structure block does not actually define a structure variable, but instead it defines the layout that such a variable would have. To define a variable with the layout specified on the structure statement, simply specify a Structure variable:		A Structure block does not actually define a structure variable, but instead it defines the layout that such a variable would have. To define a variable with the layout specified on the structure statement, simply specify a Structure variable:
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	end structure		end structure

	All Structure variables of type Budgie would have to end in the characters “.parakeet”, making it relatively east to detect references to this type of variable in User Language code:		All Structure variables of type Budgie would have to end in the characters “.parakeet”, making it relatively east to detect references to this type of variable in <var class="product">User Language</var> code:
	%my.parakeet:color = 'blue'		%my.parakeet:color = 'blue'
	...		...
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	==Comparing structures and classes==		==Comparing structures and classes==
	Structures and structure variables provide a rich new facility to User Language programmers. Yet, oddly, the recommendation is to use them sparingly, and in general, to use Classes and Object variables instead. There are many reasons for this:		Structures and structure variables provide a rich new facility to <var class="product">User Language</var> programmers. Yet, oddly, the recommendation is to use them sparingly, and in general, to use Classes and Object variables instead. There are many reasons for this:

	* Assignment of object variables is much more efficient because only the reference (pointer) is actually copied, not all the values.		* Assignment of object variables is much more efficient because only the reference (pointer) is actually copied, not all the values.

JAL2: /* See also */

2012-01-11T18:12:07Z

JAL2 at 16:55, 11 January 2012

2012-01-11T16:55:12Z

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	<li>[[Getting started with object-oriented programming for User Language programmers]]		<li>[[Getting started with object-oriented programming for User Language programmers]]
	</ul>		</ul>

			[[Category:Janus SOAP ULI topics]]

JAL2 at 00:15, 31 August 2011

2011-08-31T00:15:12Z

← Older revision		Revision as of 00:15, 31 August 2011
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	A '''structure''' is, as the name suggests, a layout of standard User Language variables.		A '''structure''' is, as the name suggests, a layout of standard User Language variables.

	The layout of a structure is described by a Structure block and variables with that layout are indicated by the Structure datatype on variable declarations.		The layout of a structure is described by a Structure block, and variables with that layout are indicated by the Structure datatype on variable declarations.

			==Structure blocks and variable declaration==
	A Structure block has the following syntax:		A Structure block has the following syntax:

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	Structures also differ significantly from Images in that multiple variables can be declared with the same structure and that structure variables can be assigned to each other as a whole, rather than a member at a time:		Structures also differ significantly from Images in that multiple variables can be declared with the same structure and that structure variables can be assigned to each other as a whole, rather than a member at a time:

	%sunshine is structure budgie		<p class="code">%sunshine is structure budgie
	%tweetie is structure budgie		%tweetie is structure budgie
	%sunshine:color = 'blue'
	%sunshine:size = 18		%sunshine:color = 'blue'
	%tweetie = %sunshine		%sunshine:size = 18
			%tweetie = %sunshine </p>

	Note: Structure assignment is assignment by value: the elements of the source structure are copied one by one (very efficiently) to the target structure, so that subsequent changes to the source structure variable do not affect the target.		'''Note:''' Structure assignment is assignment by value: the elements of the source structure are copied one by one (very efficiently) to the target structure, so that subsequent changes to the source structure variable do not affect the target.

	For example, the following code would print “blue”,		For example, the following code would print “blue”,
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	in contrast to the behavior of object variables, described later, where assignment is by reference.		in contrast to the behavior of object variables, described later, where assignment is by reference.

			==Working with structure variables==
	Structure variables can be passed as both input and output subroutine parameters:		Structure variables can be passed as both input and output subroutine parameters:

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	%sunshine = %budgieTemplate		%sunshine = %budgieTemplate

	The ~~requiredSuffix~~ parameter on structure definitions, like the corresponding parameter on class definitions, provides a way of enforcing naming standards for structure variable names. For example, if you have a structure definition like this:		==The RequiredSuffix parameter==
			The <var>RequiredSuffix</var> parameter on structure definitions, like the corresponding parameter on class definitions, provides a way of enforcing naming standards for structure variable names. For example, if you have a structure definition like this:

	structure budgie requiredSuffix=.parakeet		structure budgie requiredSuffix=.parakeet
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	%current.parakeet = %my.parakeet		%current.parakeet = %my.parakeet

			==Comparing structures and classes==
	Structures and structure variables provide a rich new facility to User Language programmers. Yet, oddly, the recommendation is to use them sparingly, and in general, to use Classes and Object variables instead. There are many reasons for this:		Structures and structure variables provide a rich new facility to User Language programmers. Yet, oddly, the recommendation is to use them sparingly, and in general, to use Classes and Object variables instead. There are many reasons for this:

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	* Any data structure that represents an attribute of an object or method — an adjective, if you will — might make sense as a Structure.		* Any data structure that represents an attribute of an object or method — an adjective, if you will — might make sense as a Structure.
	* Because structures are statically allocated in VTBL, accessing data in a structure can be somewhat more efficient than accessing data in an object (and in an image, incidentally), so might be useful in cases where performance of individual member access is the paramount concern.		* Because structures are statically allocated in VTBL, accessing data in a structure can be somewhat more efficient than accessing data in an object (and in an image, incidentally), so might be useful in cases where performance of individual member access is the paramount concern.

			==See also==
			<ul>
			<li>[[Classes and Objects]]
			<li>[[Object variables]]
			<li>[[Copying objects]]
			<li>[[Global and session objects]]
			<li>[[Managing server space for objects]]
			<li>[[Methods]]
			<li>[[Lists of classes and methods]]
			<li>[[Enumerations]]
			<li>[[Janus SOAP User Language Interface\|Janus SOAP ULI]]
			<li>[[Getting started with object-oriented programming for User Language programmers]]
			</ul>

← Older revision		Revision as of 22:10, 14 October 2013
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	<li>[[Object variables]]		<li>[[Object variables]]
	<li>[[Methods]]		<li>[[Methods]]
	<li>[[~~Janus SOAP ULI essentials~~]]		<li>[[Object oriented programming in SOUL]]
	</ul>		</ul>

	[[Category:SOUL object-oriented programming topics]]		[[Category:SOUL object-oriented programming topics]]

← Older revision		Revision as of 18:12, 11 January 2012
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	<li>[[Classes and Objects]]		<li>[[Classes and Objects]]
	<li>[[Object variables]]		<li>[[Object variables]]
	~~<li>[[Copying objects]]~~
	~~<li>[[Global and session objects]]~~
	~~<li>[[Managing server space for objects]]~~
	<li>[[Methods]]		<li>[[Methods]]
	~~<li>[[Lists of classes and methods]]~~		<li>[[Janus SOAP essentials]]
	~~<li>[[Enumerations]]~~
	<li>[[Janus SOAP ~~User Language Interface\|Janus SOAP ULI]]~~
	~~<li>[[Getting started with object-oriented programming for User Language programmers~~]]
	</ul>		</ul>

	[[Category:Janus SOAP ULI topics]]		[[Category:Janus SOAP ULI topics]]