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R6 queue class

Source: R/crew_queue.R
crew_class_queue.Rd

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.

See also

Other queue: crew_queue()

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

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.

Examples

crew_queue()
#> <crew_class_queue>
#>   Public:
#>     clean: function () 
#>     collect: function () 
#>     data: active binding
#>     empty: function () 
#>     extend: function (n) 
#>     head: active binding
#>     initialize: function (data = NULL, step = NULL) 
#>     list: function () 
#>     nonempty: function () 
#>     pop: function (n = 1L) 
#>     private: environment
#>     push: function (x) 
#>     reset: function () 
#>     self: crew_class_queue, R6
#>     set: function (data = character(0L)) 
#>     step: active binding
#>     tail: active binding
#>     validate: function () 
#>   Private:
#>     .data: 
#>     .head: 1
#>     .step: 1000
#>     .tail: 0