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Queue/Usage: Difference between revisions
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=={{header|Ada}}==
<lang ada>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;</lang>
</lang>▼
Sample output:
<pre>Is_Empty TRUE</pre>
</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 <cassert> // for run time assertions
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q.pop();
assert( q.empty() );
▲}</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
<lang cpp> std::queue<int, std::list<int> ></lang>▼
▲ std::queue<int, std::list<int> >
(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().
{fifo,[],[]}
2> fifo:empty(Q).
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8> fifo:pop(fifo:new()).
** exception error: 'empty fifo'
in function fifo:pop/1</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'
isEmpty__queue ''
1
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isEmpty__queue ''
1</lang>
=={{header|Java}}==
{{works with|Java|1.5+}}
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.Queue;
...
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System.out.println(queue.remove()); // 1
System.out.println(queue); // [2, 3]
System.out.println(queue.isEmpty()); // false</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.
{{works with|Java|1.4}}
<lang java>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</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:
false
2
true
undefined</pre>
=={{header|Logo}}==
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UCB Logo comes with a protocol for treating lists as queues.
print empty? :fifo ; true
queue "fifo 1
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print dequeue "fifo ; 1
show :fifo ; [2 3]
print empty? :fifo ; false</lang>
=={{header|OCaml}}==
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=={{header|Python}}==
<lang python>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</lang>
=={{header|Ruby}}==
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