Queue/Definition: Difference between revisions

=={{header|Elena}}==

ELENA 3.2.1 :

<lang elena>import extensions.

template queue :: type

{

array<type> theArray.

int theTop.

int theTale.

explicit

[

theArray := type&(8).

theTop := 0.

theTale := 0.

]

// explicit int:capacity

// [

// theArray := list<type>(capacity).

// theTop := 0.

// theTale := 0.

// ]

bool empty

= theTop == theTale.

push type:anObject

[

if (theTale > theArray length)

[

theArray := theArray reallocate(theTale).

].

theArray[theTale] := anObject.

theTale += 1.

]

type pop

[

if (theTale == theTop)

[ InvalidOperationException new:"Queue is empty"; raise ].

type item := theArray[theTop].

theTop += 1.

^ item

]

}

program =

[

queue<int> q := queue<int>.

q push(1).

q push(2).

q push(3).

console printLine(q pop).

console printLine(q pop).

console printLine(q pop).

console printLine("a queue is ", q empty; iif("empty","not empty")).

console print("Trying to pop:").

try(q pop)

{

on(Exception e)

[

console printLine(e message)

]

}

].</lang>

{{out}}

<pre>

1

2

3

a queue is empty

Trying to pop:Queue is empty

</pre>