While loop - Revision history

Logmanoriginal: Logmanoriginal moved page While Loop structure to While loop: Only the first word in a title should start with a capital letter

2023-05-07T15:01:47Z

Logmanoriginal moved page While Loop structure to While loop: Only the first word in a title should start with a capital letter

← Older revision	Revision as of 15:01, 7 May 2023
(No difference)

Q at 12:38, 25 June 2020

2020-06-25T12:38:15Z

← Older revision		Revision as of 12:38, 25 June 2020
Line 1:		Line 1:
	{{TOCright}}		{{TOCright}}
	{{LabVIEW Palette Object Information\|palette=Functions Palette/Programming/Structures{{!}}Structures palette\|type=structure}}		{{LabVIEW Palette Object Information\|palette=Functions Palette/Programming/Structures{{!}}Structures palette\|type=structure\|icon=Functions Palette - Programming - Structures - While Loop.png}}
	[[File:While Loop - Components.png\|thumb\|Components of a While Loop]]		[[File:While Loop - Components.png\|thumb\|Components of a While Loop]]

Q: Reorganized page

2020-06-23T19:57:51Z

Reorganized page

← Older revision		Revision as of 19:57, 23 June 2020
Line 1:		Line 1:
			{{TOCright}}
			{{LabVIEW Palette Object Information\|palette=Functions Palette/Programming/Structures{{!}}Structures palette\|type=structure}}
	[[File:While Loop - Components.png\|thumb\|Components of a While Loop]]		[[File:While Loop - Components.png\|thumb\|Components of a While Loop]]

	A While Loop is a primitive [[Functions Palette/Programming/Structures\|structure]] that repeats the code within its [[Subdiagram\|subdiagram]] until a [[Boolean]] condition is met. The code within its subdiagram is executed at least once. It runs endlessly if the condition is not met.		A '''While Loop''' is a primitive [[Functions Palette/Programming/Structures\|structure]] that repeats the code within its [[Subdiagram\|subdiagram]] until a [[Boolean]] condition is met. The code within its subdiagram is executed at least once. It runs endlessly if the condition is not met.

	~~<br clear~~=~~"all">~~		== Usage ==
	== Boolean condition ==		=== Boolean condition ===

	[[File:While Loop - Conditional Terminal - Right Click Menu.png\|thumb\|Conditional terminal right-click menu]]		[[File:While Loop - Conditional Terminal - Right Click Menu.png\|thumb\|Conditional terminal right-click menu]]
Line 26:		Line 28:
	A loop that never meets its condition is called an [[#Infinite loop\|infinite loop]].		A loop that never meets its condition is called an [[#Infinite loop\|infinite loop]].

	~~<br clear~~=~~"all">~~		=== Infinite loop ===
	== Infinite loop ==

	An infinite loop is a loop where the stop condition is never met. The simplest form of infinite loop is achieved by wiring a [[File:BooleanFalse2010.png\|frameless\|border\|False]] constant to the conditional terminal.		An infinite loop is a loop where the stop condition is never met. The simplest form of infinite loop is achieved by wiring a [[File:BooleanFalse2010.png\|frameless\|border\|False]] constant to the conditional terminal.
Line 38:		Line 39:
	Infinite loops will never stop and can cause a program to be unresponsive to user input. Most cases of infinite loops are not intentional and the result of bugs. A typical mistake is wiring a Boolean value from outside the loop to the conditional terminal. Since input tunnels are evaluated ''before'' the first iteration, the Boolean value always stays the same. This causes the While Loop to execute its subdiagram exactly once if the Boolean value is [[File:BooleanTrue2010.png\|frameless\|border\|True]] and endlessly if the Boolean value is [[File:BooleanFalse2010.png\|frameless\|border\|False]].		Infinite loops will never stop and can cause a program to be unresponsive to user input. Most cases of infinite loops are not intentional and the result of bugs. A typical mistake is wiring a Boolean value from outside the loop to the conditional terminal. Since input tunnels are evaluated ''before'' the first iteration, the Boolean value always stays the same. This causes the While Loop to execute its subdiagram exactly once if the Boolean value is [[File:BooleanTrue2010.png\|frameless\|border\|True]] and endlessly if the Boolean value is [[File:BooleanFalse2010.png\|frameless\|border\|False]].

	~~<br clear~~=~~"all">~~		=== Execution speed ===
	== Execution speed ==

	While Loops execute as fast as possible and therefore can be a cause for high [[Wikipedia:CPU\|CPU]] load. For this reason While Loops should be throttled by using the [[Functions Palette/Programming/Timing/Wait (ms)\|Wait (ms)]] function with a delay time that is appropriate for the task.		While Loops execute as fast as possible and therefore can be a cause for high [[Wikipedia:CPU\|CPU]] load. For this reason While Loops should be throttled by using the [[Functions Palette/Programming/Timing/Wait (ms)\|Wait (ms)]] function with a delay time that is appropriate for the task.
Line 49:		Line 49:
	Note that limiting the execution speed does '''not''' guarantee that the loop is executed at exact intervals. The loop can still execute slower if the code takes longer to execute, or the [[Wikipedia:Operating system\|operating system]] pauses execution. Use [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]] for time-critical tasks.		Note that limiting the execution speed does '''not''' guarantee that the loop is executed at exact intervals. The loop can still execute slower if the code takes longer to execute, or the [[Wikipedia:Operating system\|operating system]] pauses execution. Use [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]] for time-critical tasks.

	== Nomenclature controversy ==		=== Nomenclature controversy ===

	Strictly speaking the While Loop is a [[Wikipedia:Do while loop\|Do While Loop]], because the stop condition is checked at the end of a loop, which requires the subdiagram to execute at least once. A "real" While Loop, however, would first check the stop condition and execute the subdiagram only if the condition is not met. This can be confusing to programmers that are familiar with other programming languages and that are new to LabVIEW.		Strictly speaking the While Loop is a [[Wikipedia:Do while loop\|Do While Loop]], because the stop condition is checked at the end of a loop, which requires the subdiagram to execute at least once. A "real" While Loop, however, would first check the stop condition and execute the subdiagram only if the condition is not met. This can be confusing to programmers that are familiar with other programming languages and that are new to LabVIEW.
Line 61:		Line 61:

	* Wire an [[error cluster]] to the conditional terminal to terminate the loop on an error.		* Wire an [[error cluster]] to the conditional terminal to terminate the loop on an error.

			== History ==
			{{ambox\|text=History information is needed. What changes have occurred over previous versions?}}
			{\| class="wikitable"
			! Version
			! Change(s)
			\|-
			\|[[File:LV2018.png\|frameless\|border\|64x64px\|LabVIEW 2018\|link=LabVIEW 2018]]
			\|More info to come.
			\|}

	== See also ==		== See also ==
	* [[WhileLoop class]]		* [[WhileLoop class]]
	* [[~~Functions Palette/Programming/Structures/Timed Structures/~~Timed Loop\|Timed Loops]]		* [[Timed Loop structure\|Timed Loops]]

			== External Links ==
			{{ambox\|text=Add links to external resources that would also help.}}

	[[Category:Structures Palette]]		[[Category:Structures Palette]]
	[[Category:While Loop]]		[[Category:While Loop]]

Q: Q moved page Functions Palette/Programming/Structures/While Loop to While Loop structure: Renaming to make it more in line with other palette items.

2020-06-23T18:28:36Z

Q moved page Functions Palette/Programming/Structures/While Loop to While Loop structure: Renaming to make it more in line with other palette items.

← Older revision	Revision as of 18:28, 23 June 2020
(No difference)

Logmanoriginal: Add to Structures Palette

2020-05-15T13:26:13Z

Add to Structures Palette

← Older revision		Revision as of 13:26, 15 May 2020
Line 66:		Line 66:
	* [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]]		* [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]]

	[[Category:Structures]]		[[Category:Structures Palette]]
	[[Category:While Loop]]		[[Category:While Loop]]

Logmanoriginal: Add tips and tricks

2020-05-13T19:54:03Z

Add tips and tricks

← Older revision		Revision as of 19:54, 13 May 2020
Line 57:		Line 57:
	* Use [[Functions Palette/Programming/Structures/For Loop\|For Loops]] if the number of iterations is predictable or can be calculated.		* Use [[Functions Palette/Programming/Structures/For Loop\|For Loops]] if the number of iterations is predictable or can be calculated.
	* Use [[Functions Palette/Programming/Timing/Wait (ms)\|Wait (ms)]] to limit the execution speed of a While Loop.		* Use [[Functions Palette/Programming/Timing/Wait (ms)\|Wait (ms)]] to limit the execution speed of a While Loop.

			== Tips and tricks ==

			* Wire an [[error cluster]] to the conditional terminal to terminate the loop on an error.

	== See also ==		== See also ==

Q: /* See also */

2019-09-02T03:41:32Z

Logmanoriginal: /* Nomenclature controversy */ Fix typo

2019-07-26T14:55:40Z

Nomenclature controversy: Fix typo

← Older revision		Revision as of 14:55, 26 July 2019
Line 51:		Line 51:
	== Nomenclature controversy ==		== Nomenclature controversy ==

	Strictly speaking the While Loop is a [[Wikipedia:Do while loop\|Do While Loop]], because the stop condition is checked at the end of a loop, which requires the subdiagram to execute at least once. A "real" While Loop, however, would first check the stop condition and execute the subdiagram only if the condition is not met. This can be ~~confusion~~ to programmers that are familiar with other programming languages and that are new to LabVIEW.		Strictly speaking the While Loop is a [[Wikipedia:Do while loop\|Do While Loop]], because the stop condition is checked at the end of a loop, which requires the subdiagram to execute at least once. A "real" While Loop, however, would first check the stop condition and execute the subdiagram only if the condition is not met. This can be confusing to programmers that are familiar with other programming languages and that are new to LabVIEW.

	== Best practice ==		== Best practice ==

Logmanoriginal: Major rewrite

2019-07-26T14:52:52Z

Major rewrite

@@ Line 1: / Line 1: @@
-== What does 0ms wait function do in a while loop ==
+[[File:While Loop - Components.png|thumb|Components of a While Loop]]
-But what does a wait of 0 ms do? Let's consider the LV execution system to be a xerox copying machine. Everyone that has something to copy heads for the copying machine and lines up. If you have never had the pleasure of waiting at a copy machine, then consider any other time consuming task where people wait in line. Everytime a LV diagram executes a wait function, it is like releasing the copier and staying out of the line for some time delay. After the delay has passed, you will get back in line to make your next copy. A wait of 0 ms is like immediately going to the end of the line to let a smaller copy-task take place. If nobody is in line behind you, you immediately start your next copy task. If someone is in line, it lets them take a turn.
+A While Loop is a primitive [[Functions Palette/Programming/Structures|structure]] that repeats the code within its [[Subdiagram|subdiagram]] until a [[Boolean]] condition is met. The code within its subdiagram is executed at least once. It runs endlessly if the condition is not met.
-This 0 ms wait is a pretty cool little trick to make LabVIEW loop parallelism less chunky. It naturally adds some overhead because the loops have some setup time, but when the loops are doing significant work it is tiny. Use it whenever you think you need to, but beware that if some loops don't have any delay, they are still going to
+<br clear="all">
-hog the CPU, and the wait of 0 ms may turn into much larger waits because the loops with no waits play by different rules.
+[[File:While Loop - Conditional Terminal - Right Click Menu.png|thumb|Conditional terminal right-click menu]]
-== Is the while loop really a while loop? ==
+A Boolean value must be connected to the conditional terminal [[File:Conditional Terminal - Stop if True.png|frameless|border|Conditional Terminal]] of the loop. The condition can be changed at the conditional terminal, via the right-click menu options "Stop if True" and "Continue if True", or by clicking on the terminal.
-To create a "real" while loop wire the output of your terminating condition to a case structure surrounding the rest of the code within the loop.
+{| class="wikitable"
-This is of course true, but then there is no real difference between a while loop as you describe it and a for loop in C either. Of course the syntax changes but the functionality is really equivalent.
+A loop that never meets its condition is called an [[#Infinite loop|infinite loop]].
-Also true, but then you lose the advantage of having a shift register from the loop hold variable(s) that are part of the exit test, unless you wrap the whole thing in another loop.
+<br clear="all">
-[QUOTE]
+An infinite loop is a loop where the stop condition is never met. The simplest form of infinite loop is achieved by wiring a [[File:BooleanFalse2010.png|frameless|border|False]] constant to the conditional terminal.
-This is a little misleading, particularly for new [[LabVIEW]] programmers. The boolean test for continuation is done as soon as possible... it only waits until the end of loop execution if there is a data dependency. With no dependacy, the loop will decide whether to execute again before/in parallel with any other code in the loop.
+[[File:While Loop - Infinite Loop.png|frameless|border]]
-[[Category:structures]]
+[[File:While Loop - Infinite Loop - Beginner Mistake 1.png|thumb|A common reason for infinite loops: Wiring Boolean values from outside the loop]]

Logmanoriginal: Logmanoriginal moved page While Loop to Functions Palette/Programming/Structures/While Loop: This page explains an element from the Functions Palette

2019-07-21T19:00:40Z

Logmanoriginal moved page While Loop to Functions Palette/Programming/Structures/While Loop: This page explains an element from the Functions Palette

← Older revision	Revision as of 19:00, 21 July 2019
(No difference)

← Older revision		Revision as of 03:41, 2 September 2019
Line 59:		Line 59:

	== See also ==		== See also ==
			* [[WhileLoop class]]
	* [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]]		* [[Functions Palette/Programming/Structures/Timed Structures/Timed Loop\|Timed Loops]]

	[[Category:Structures]]		[[Category:Structures]]
	[[Category:While Loop]]		[[Category:While Loop]]