Queue/Usage: Difference between revisions

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=={{header|Ada}}==

<lang ada>with FIFO;

with FIFO;

with Ada.Text_Io; use Ada.Text_Io;

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Pop (Queue, Value);

Put_Line ("Is_Empty " & Boolean'Image (Is_Empty (Queue)));

end Queue_Test;

end Queue_Test;</lang>

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</lang>

Sample output:

<pre>

<pre>Is_Empty TRUE</pre>

Is_Empty TRUE

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</pre>

=={{header|AutoHotkey}}==

ahk forum: [http://www.autohotkey.com/forum/viewtopic.php?t=44657&postdays=0&postorder=asc&start=133 discussion]

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exit(0);

}</lang>

=={{header|C++}}==

Note that with C++'s standard queue, accessing the first element of the queue and removing it are two separate operations, <tt>front()</tt> and <tt>pop()</tt>.

<lang cpp>#include <queue>

#include <queue>

#include <cassert> // for run time assertions

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q.pop();

assert( q.empty() );

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}</lang>

}

</lang>

Note that the container used to store the queue elements can be specified explicitly; to use a linked linst instead of a deque (the latter is the default), just replace the definition of <tt>q</tt> to

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<lang cpp> std::queue<int, std::list<int> ></lang>

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std::queue<int, std::list<int> >

</lang>

(and add <tt>#include <list></tt>, of course). Also note that the containers can be used directly; in that case <tt>push</tt> and <tt>pop</tt> have to be replaced by <tt>push_back</tt> and <tt>pop_front</tt>.

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=={{header|Erlang}}==

All functions, from the shell:

<lang Erlang>1> Q = fifo:new().

1> Q = fifo:new().

{fifo,[],[]}

2> fifo:empty(Q).

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8> fifo:pop(fifo:new()).

** exception error: 'empty fifo'

in function fifo:pop/1

in function fifo:pop/1</lang>

</lang>

Crashing is the normal expected behavior in Erlang: let it crash, a supervisor will take responsibility of restarting processes, or the caller will take care of it. Only program for the successful cases.

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end program FIFOTest</lang>

=={{header|J}}==

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This is an interactive J session:

<lang J> queue=: conew 'fifo'

queue=: conew 'fifo'

isEmpty__queue ''

1

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isEmpty__queue ''

1</lang>

=={{header|Java}}==

LinkedList can always be used as a queue or stack, but not in conjunction with the Stack object provided by Java. To use a LinkedList as a stack, use the <tt>push</tt> and <tt>pop</tt> methods. A LinkedList can also be used as a double-ended queue (deque); LinkedList has implemented the Deque interface since Java 1.6+.

<lang java>import java.util.LinkedList;

import java.util.LinkedList;

import java.util.Queue;

...

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System.out.println(queue.remove()); // 1

System.out.println(queue); // [2, 3]

System.out.println(queue.isEmpty()); // false

System.out.println(queue.isEmpty()); // false</lang>

</lang>

You can also use "offer" and "poll" methods instead of "add" and "remove", respectively. They indicate errors with the return value instead of throwing an exception.

<lang java>import java.util.LinkedList;

import java.util.LinkedList;

...

LinkedList queue = new LinkedList();

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System.out.println(queue.removeFirst()); // 1

System.out.println(queue); // [2, 3]

System.out.println(queue.isEmpty()); // false

System.out.println(queue.isEmpty()); // false</lang>

</lang>

=={{header|JavaScript}}==

<lang javascript>var f = new FIFO();

print(f.empty());

f.push(1);

f.push(2);

f.pop();

print(f.empty());

print(f.dequeue())

print(f.empty());

print(f.dequeue());</lang>

outputs:

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<pre>true

false

2

true

undefined</pre>

=={{header|Logo}}==

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UCB Logo comes with a protocol for treating lists as queues.

make "fifo []

<lang logo> make "fifo []

print empty? :fifo ; true

queue "fifo 1

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print dequeue "fifo ; 1

show :fifo ; [2 3]

print empty? :fifo ; false

print empty? :fifo ; false</lang>

=={{header|OCaml}}==

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=={{header|Python}}==

<lang python>import Queue

import Queue

my_queue = Queue.Queue()

my_queue.put("foo")

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print my_queue.get() # foo

print my_queue.get() # bar

print my_queue.get() # baz

print my_queue.get() # baz</lang>

</lang>

=={{header|Ruby}}==