crew_class_queue: 'R6' queue class

In crew: A Distributed Worker Launcher Framework

R6 queue class

Description

R6 class for a queue.

Details

See the Details section of crew_queue(). The R6 crew queue class is not portable (for efficiency), so other packages should not inherit from it. The reason for non-portability is efficiency: elements can be directly accessed without ⁠self$⁠ or ⁠private$⁠, and they can be directly modified with ⁠<<-⁠. This is especially important for push() because envir$vector[slice] <- x copies the entire vector in memory, which has O(n^2) complexity and is extremely slow for large vectors.

Active bindings

data

See crew_queue().

head

Non-negative integer pointing to the location of the next element to pop.

tail

Non-negative integer pointing to the tail of the queue.

step

See crew_queue().

Methods

Public methods

• crew_class_queue$new()

• crew_class_queue$validate()

• crew_class_queue$empty()

• crew_class_queue$nonempty()

• crew_class_queue$list()

• crew_class_queue$reset()

• crew_class_queue$clean()

• crew_class_queue$set()

• crew_class_queue$extend()

• crew_class_queue$push()

• crew_class_queue$pop()

• crew_class_queue$collect()

---

Method new()

Create a queue object.

Usage

crew_class_queue$new(data = NULL, step = NULL)

Arguments

data

See crew_queue().

step

See crew_queue().

Returns

A queue object.

---

Method validate()

Validate the queue.

Usage

crew_class_queue$validate()

Returns

NULL (invisibly). Called for its side effects.

---

Method empty()

Check if the queue is empty.

Usage

crew_class_queue$empty()

Returns

TRUE if the queue is empty, FALSE otherwise.

---

Method nonempty()

Check if the queue is empty.

Usage

crew_class_queue$nonempty()

Returns

TRUE if the queue is nonempty, FALSE otherwise.

---

Method list()

List available data.

Usage

crew_class_queue$list()

Returns

Character vector of available data.

---

Method reset()

Reset the queue.

Usage

crew_class_queue$reset()

Returns

NULL (invisibly). Called for its side effects.

---

Method clean()

Remove popped elements from the data in the queue.

Usage

crew_class_queue$clean()

Returns

NULL (invisibly).

---

Method set()

Set the data in the queue.

Usage

crew_class_queue$set(data = character(0L))

Arguments

data

Character vector of data to set.

Returns

NULL (invisibly). Called for its side effects.

---

Method extend()

Extend the queue data by step elements.

Usage

crew_class_queue$extend(n)

Arguments

n

Positive integer, number of elements to extend the queue data.

Returns

NULL (invisibly).

---

Method push()

Append new elements to the queue.

Usage

crew_class_queue$push(x)

Arguments

x

Character vector of new data to append.

Details

push() is the reason the queue class is not portable. According to R6 documentation, members of non-portable classes can be accessed without ⁠self$⁠ or ⁠private$⁠, and assignment can be done with ⁠<<-⁠. In the case of push(), this prevents each assignment from deep-copying the entire contents of the vector.

Returns

NULL (invisibly).

---

Method pop()

Pop one or more elements off the queue.

Usage

crew_class_queue$pop(n = 1L)

Arguments

n

Positive integer, maximum number of elements to pop. Fewer than n are popped if fewer than n are available.

Returns

Character vector of elements popped off the queue. NULL if there are no more elements available to pop.

---

Method collect()

Remove and return all available elements off the queue.

Usage

crew_class_queue$collect()

Returns

Character vector, elements collected from the queue. NULL if there are no more elements available to collect.

See Also

Other queue: crew_queue()

Examples

crew_queue()

crew documentation built on June 9, 2025, 5:09 p.m.