Dequeue (Function)

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Operating mode for a multithread management

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Dequeue (Function)

In french: Défile

Dequeues an element from a queue. The element is deleted from the queue and returned in the specified variable.

Versions 18 and later

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

New in version 18

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

This function is now available in Windows Store apps mode.

This function is now available for iPhone/iPad applications.

Versions 21 and later

This function is now available in Apple Watch mode.

This function is now available for Java applications.

This function is now available for Android applications.

This function is now available in Android Widget mode.

This function is now available in Universal Windows 10 App mode.

New in version 21

This function is now available in Apple Watch mode.

This function is now available for Java applications.

This function is now available for Android applications.

This function is now available in Android Widget mode.

This function is now available in Universal Windows 10 App mode.

This function is now available in Apple Watch mode.

This function is now available for Java applications.

This function is now available for Android applications.

This function is now available in Android Widget mode.

This function is now available in Universal Windows 10 App mode.

Example

MyQueue is Queue of int

// Enqueues the values 1, 2 and 3
Enqueue(MyQueue, 1)
Enqueue(MyQueue, 2)
Enqueue(MyQueue, 3)

// Display the trace: 1, 2, 3
x is int
WHILE Dequeue(MyQueue, x)
Trace(x)
END

Syntax

Retrieving the element at the beginning of queue Hide the details

<Result> = Dequeue(<Queue> [, <Element>])

<Result>: Boolean

True if the element was dequeued,
False if the queue is empty.

<Queue>: Queue

Name of the Queue variable to use.

<Element>: Type of elements handled by the queue, optional parameter

Name of variable into which the value of dequeued element is returned. If this parameter is not specified, the element is dequeued but its value is not retrieved.

Retrieving the element at the beginning of queue (multithread syntax) Hide the details

<Result> = Dequeue(<Queue> [, <Element> [, <Options> [, <Timeout>]]])

<Result>: Boolean

True if the element was dequeued,
False if the time-out is exceeded (<Time-out> parameter) or if ..AdditionCompleted becomes True.

<Queue>: Queue

Name of the Queue variable to use.

<Element>: Type of elements handled by the queue, optional parameter

Name of variable into which the value of dequeued element is returned. If this parameter is not specified, the element is dequeued but its value is not retrieved.

<Options>: Optional Integer constant

Option for managing the queue:
WaitIfEmpty Waits for an element to be added into the queue by another thread.

<Timeout>: Optional integer or optional Duration

Maximum time-out expressed in hundredths of a second. This parameter can correspond to:
an integer corresponding to the number of hundredths of a second,
a Duration variable,
Versions 23 and later
the direct indication of duration (1 s or 10 ms for example).
New in version 23
the direct indication of duration (1 s or 10 ms for example).
the direct indication of duration (1 s or 10 ms for example).
This parameter corresponds to the Infinite constant by default (no maximum time-out).

Remarks

Operating mode for a multithread management

If an element is found in the queue, it is deleted from the queue and returned by the <Element> parameter by reference.

If the queue is empty, Dequeue waits for an element to be added into the queue. The maximum time-out can be specified by the <Timeout> parameter.

The function returns True if an element was dequeued, False if the time-out is exceeded or if ..AdditionCompleted becomes True.

..NbPendingThread returns the number of pending threads.

The assignment of ..AdditionCompleted to True provokes the end of the time-out for all the pending threads. In this case, Dequeue returns False.

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