Boolean enumeration - Revision history

JAL: add "See also" section

2018-04-23T16:35:40Z

add "See also" section

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	</table>		</table>

	[[~~Category:SOUL object-~~oriented programming ~~topics~~]]		==See also==
			<ul>
			<li>[[Lists of classes and methods#Enumerations\|List of system enumerations]] </li>
			<li>[[Object oriented programming in SOUL]] </li>
			</ul>

JAL: add category

2018-04-20T18:48:17Z

add category

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	<td>A <var>Boolean</var> enumeration variable or an expression that results in a <var>Boolean</var> enumeration.</td></tr>		<td>A <var>Boolean</var> enumeration variable or an expression that results in a <var>Boolean</var> enumeration.</td></tr>
	</table>		</table>

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

JAL: /* IsTrue function */

2014-07-23T19:03:54Z

IsTrue function

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	With automatic conversion of numbers to <var>Boolean</var> targets in version 8.1 of the <var class="product">Sirius Mods</var>, assignment of a <var>Boolean</var> value to a numeric target can be rare.		With automatic conversion of numbers to <var>Boolean</var> targets in version 8.1 of the <var class="product">Sirius Mods</var>, assignment of a <var>Boolean</var> value to a numeric target can be rare.

	In addition to the example in [[#Booleans not automatically converted to numbers\|"Booleans not automatically converted to numbers"]], here is an example which generates some C code, using a <var>Boolean</var> in a string context:		In addition to the example in [[#Booleans not automatically converted to numbers\|Booleans not automatically converted to numbers]], here is an example which generates some C code, using a <var>Boolean</var> in a string context:
	<p class="code">%bool is boolean		<p class="code">%bool is boolean
	...		...

JAL: /* IsFalse syntax */

2014-07-23T19:03:22Z

IsFalse syntax

← Older revision		Revision as of 19:03, 23 July 2014
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	With automatic conversion of numbers to <var>Boolean</var> targets in version 8.1 of the <var class="product">Sirius Mods</var>, assignment of a <var>Boolean</var> value to a numeric target can be rare.		With automatic conversion of numbers to <var>Boolean</var> targets in version 8.1 of the <var class="product">Sirius Mods</var>, assignment of a <var>Boolean</var> value to a numeric target can be rare.
	See the examples in [[#Booleans not automatically converted to numbers\|"Booleans not automatically converted to numbers"]] and in [[#IsTrue function\|"IsTrue function"]].		See the examples in [[#Booleans not automatically converted to numbers\|Booleans not automatically converted to numbers]] and in [[#IsTrue function\|IsTrue function]].

	====Syntax terms====		====Syntax terms====

JAL: /* Enumeration methods */

2014-07-23T19:01:51Z

Enumeration methods

← Older revision		Revision as of 19:01, 23 July 2014
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	==Enumeration methods==		==Enumeration methods==
	Besides the [[#Common ~~Enumeration~~ methods\|common enumeration methods]], the		Besides the [[Enumerations#Common enumeration methods\|common enumeration methods]], the
	system <var>Boolean</var> enumeration has additional methods available, which are described here.		system <var>Boolean</var> enumeration has additional methods available, which are described here.

JAL at 18:08, 27 November 2012

2012-11-27T18:08:45Z

Show changes

JAL: /* Using logical operators with booleans */

2012-11-27T16:52:38Z

Using logical operators with booleans

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	==Using logical operators with booleans==		==Using logical operators with booleans==
	~~<var class="product">~~<var class="product">User Language~~</var>~~</var> has three logical operators:		<var class="product">User Language</var> has three logical operators:
	<ul>		<ul>
	<li>Not</li>		<li>Not</li>
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	<p class="code">if %bool and (%y gt %x) Then		<p class="code">if %bool and (%y gt %x) Then
	</p>		</p>

	==Automatic conversion of numbers to Boolean==		==Automatic conversion of numbers to Boolean==
	In <var class="product">Sirius Mods 8.1</var> and later, it is also possible to assign a number to a <var>Boolean</var> variable. When this is done, the number 0 is converted to <var>False</var> and every other value is converted to <var>True</var>. This is especially useful for assigning the result of a comparison to a boolean:		In <var class="product">Sirius Mods 8.1</var> and later, it is also possible to assign a number to a <var>Boolean</var> variable. When this is done, the number 0 is converted to <var>False</var> and every other value is converted to <var>True</var>. This is especially useful for assigning the result of a comparison to a boolean:

JALWiccan: 1 revision

2012-11-27T16:51:39Z

1 revision

← Older revision	Revision as of 16:51, 27 November 2012
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JAL at 16:51, 27 November 2012

2012-11-27T16:51:38Z

← Older revision		Revision as of 16:51, 27 November 2012
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	The '''Boolean''' enumeration implements the standard logical paradigm of "true" and "false".		The '''Boolean''' enumeration implements the standard logical paradigm of "true" and "false".

	While, in some sense, it is just like any other enumeration, because the concept of true and false is so basic to programming, <var>Boolean</var> variables are treated specially by <var class="product">User Language</var>.		While, in some sense, it is just like any other enumeration, because the concept of true and false is so basic to programming, <var>Boolean</var> variables are treated specially by <var class="product"><var class="product">User Language</var></var>.

	==Boolean enumeration values==		==Boolean enumeration values==
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	==Using logical operators with booleans==		==Using logical operators with booleans==
	<var class="product">User Language</var> has three logical operators:		<var class="product"><var class="product">User Language</var></var> has three logical operators:
	<ul>		<ul>
	<li>Not</li>		<li>Not</li>
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	<li>Or</li>		<li>Or</li>
	</ul>		</ul>
	Strictly speaking, in User Language these operators actually operate on numeric values where 0 is treated as <var>False</var> and any non-zero value is treated as <var>True</var>. However, because of the importance of boolean logic in programming, <var>Boolean</var> variables or values can be used instead of numbers for these operators. A boolean <var>True</var> is treated as 1 and a <var>False</var> value is treated as 0. As such, boolean variables can be used in logical operations as in:		Strictly speaking, in <var class="product">User Language</var> these operators actually operate on numeric values where 0 is treated as <var>False</var> and any non-zero value is treated as <var>True</var>. However, because of the importance of boolean logic in programming, <var>Boolean</var> variables or values can be used instead of numbers for these operators. A boolean <var>True</var> is treated as 1 and a <var>False</var> value is treated as 0. As such, boolean variables can be used in logical operations as in:
	<p class="code">if not %bool then		<p class="code">if not %bool then
	</p>		</p>
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	Other places where a <var>Boolean</var> value can be used, that is, where it is automatically		Other places where a <var>Boolean</var> value can be used, that is, where it is automatically
	converted to the 0 or 1 that <var class="product">User Language</var> expects are:		converted to the 0 or 1 that <var class="product"><var class="product">User Language</var></var> expects are:
	<ul>		<ul>
	<li>As a <var>Repeat</var> statement operand.		<li>As a <var>Repeat</var> statement operand.

JAL at 16:51, 27 November 2012

2012-11-27T16:51:33Z

← Older revision		Revision as of 16:51, 27 November 2012
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	The '''Boolean''' enumeration implements the standard logical paradigm of "true" and "false".		The '''Boolean''' enumeration implements the standard logical paradigm of "true" and "false".

	While, in some sense, it is just like any other enumeration, because the concept of true and false is so basic to programming, <var>Boolean</var> variables are treated specially by User Language.		While, in some sense, it is just like any other enumeration, because the concept of true and false is so basic to programming, <var>Boolean</var> variables are treated specially by <var class="product">User Language</var>.

	==Boolean enumeration values==		==Boolean enumeration values==
	The system <var>Boolean</var> enumeration values are:		The system <var>Boolean</var> enumeration values are:
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	<li><b>False</b>		<li><b>False</b>
	</ul>		</ul>
	However, like all other enumerations, a <var>Boolean</var> variable can also be unset so have a null value. While this can be useful in detecting references to unset variables, it can also be problematic in certain sitiuations. Use of the <var>Initial</var> clause on variable declarations and the <var>Default</var> clause on method parameter declarations can mitigate most of these issues, nevertheless it is important to keep in mind the possibility of a <var>Boolean</var> variable being null.		However, like all other [[Enumerations\|enumerations]], a <var>Boolean</var> variable can also be unset so have a null value. While this can be useful in detecting references to unset variables, it can also be problematic in certain sitiuations. Use of the <var>Initial</var> clause on variable declarations and the <var>Default</var> clause on method parameter declarations can mitigate most of these issues, nevertheless it is important to keep in mind the possibility of a <var>Boolean</var> variable being null.

	==Declaring boolean variables==		==Declaring boolean variables==
	Boolean variables can be declared the same way any enumeration variables are declared, with the keyword <var>Enumeration</var> followed by the class name:		<var>Boolean</var> variables can be declared the same way any enumeration variables are declared, with the keyword <var>Enumeration</var> followed by the class name:
	<p class="code>%truth is enumeration boolean		<p class="code">%truth is enumeration boolean
	</p>		</p>
	However, because boolean processing is such a basic part of any programming language, <var>Boolean</var> variables can be declared without the <var>Enumeration</var> keyword:		However, because boolean processing is such a basic part of any programming language, <var>Boolean</var> variables can be declared without the <var>Enumeration</var> keyword:
	<p class="code>%truth is boolean		<p class="code">%truth is boolean
	</p>		</p>
	This is also true for method variables and results. For example, ~~then~~ following:		This is also true for method variables and results. For example, the following:
	<p class="code">function foo(%n is float, %test is enumeration boolean) -		<p class="code">function foo(%n is float, %test is enumeration boolean) is enumeration boolean
	is enumeration boolean
	</p>		</p>
	is identical to		is identical to:
	<p class="code">function foo(%n is float, %test is boolean) is boolean		<p class="code">function foo(%n is float, %test is boolean) is boolean
	</p>		</p>

	==Using booleans in If conditions==		==Using booleans in If conditions==
	The whole point of <var>Boolean</var> variables is to be able to test them for truth and, depending on the result, perform some processing. For example, if <~~var~~>%bool</~~var~~> is a <var>Boolean</var> variable, the following performs the contents of the <var>If</var> block if <~~var~~>%bool</~~var~~> is set to <~~var~~>True</~~var~~>:		The whole point of <var>Boolean</var> variables is to be able to test them for truth and, depending on the result, perform some processing. For example, if <code>%bool</code> is a <var>Boolean</var> variable, the following statement performs the contents of the <var>If</var> block if <code>%bool</code> is set to <code>True</code>:
	<p class="code">if %bool then		<p class="code">if %bool then
	</p>		</p>
	Note that in this example, if <~~var~~>%bool</~~var~~> is not set (null), then the request would be canceled with a ~~null~~ object reference error.		Note that in this example, if <code>%bool</code> is not set (null), then the request would be canceled with a <var>Null</var> object reference error.

	==Using logical operators with booleans==		==Using logical operators with booleans==
	User ~~language~~ has three logical operators:		<var class="product">User Language</var> has three logical operators:
	<ul>		<ul>
	<li>Not</li>		<li>Not</li>