.TH "Queue" 3o source: 2019-08-06 OCamldoc "OCaml library"
.SH NAME
Queue \- First-in first-out queues.
.SH Module
Module   Queue
.SH Documentation
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Module
.BI "Queue"
 : 
.B sig  end

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First\-in first\-out queues\&.
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This module implements queues (FIFOs), with in\-place modification\&.
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Warning This module is not thread\-safe: each 
.B Queue\&.t
value
must be protected from concurrent access (e\&.g\&. with a 
.B Mutex\&.t
)\&.
Failure to do so can lead to a crash\&.

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.I type 
.B 'a
.I t 

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The type of queues containing elements of type 
.B \&'a
\&.

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.I exception Empty 

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Raised when 
.B Queue\&.take
or 
.B Queue\&.peek
is applied to an empty queue\&.

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.I val create 
: 
.B unit -> 'a t
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Return a new queue, initially empty\&.

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.I val add 
: 
.B 'a -> 'a t -> unit
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.B add x q
adds the element 
.B x
at the end of the queue 
.B q
\&.

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.I val push 
: 
.B 'a -> 'a t -> unit
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.B push
is a synonym for 
.B add
\&.

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.I val take 
: 
.B 'a t -> 'a
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.B take q
removes and returns the first element in queue 
.B q
,
or raises 
.B Queue\&.Empty
if the queue is empty\&.

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.I val pop 
: 
.B 'a t -> 'a
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.B pop
is a synonym for 
.B take
\&.

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.I val peek 
: 
.B 'a t -> 'a
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.B peek q
returns the first element in queue 
.B q
, without removing
it from the queue, or raises 
.B Queue\&.Empty
if the queue is empty\&.

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.I val top 
: 
.B 'a t -> 'a
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.B top
is a synonym for 
.B peek
\&.

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.I val clear 
: 
.B 'a t -> unit
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Discard all elements from a queue\&.

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.I val copy 
: 
.B 'a t -> 'a t
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Return a copy of the given queue\&.

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.I val is_empty 
: 
.B 'a t -> bool
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Return 
.B true
if the given queue is empty, 
.B false
otherwise\&.

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.I val length 
: 
.B 'a t -> int
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Return the number of elements in a queue\&.

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.I val iter 
: 
.B ('a -> unit) -> 'a t -> unit
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.B iter f q
applies 
.B f
in turn to all elements of 
.B q
,
from the least recently entered to the most recently entered\&.
The queue itself is unchanged\&.

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.I val fold 
: 
.B ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b
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.B fold f accu q
is equivalent to 
.B List\&.fold_left f accu l
,
where 
.B l
is the list of 
.B q
\&'s elements\&. The queue remains
unchanged\&.

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.I val transfer 
: 
.B 'a t -> 'a t -> unit
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.B transfer q1 q2
adds all of 
.B q1
\&'s elements at the end of
the queue 
.B q2
, then clears 
.B q1
\&. It is equivalent to the
sequence 
.B iter (fun x \-> add x q2) q1; clear q1
, but runs
in constant time\&.

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