Queue: a first in, first out data structure

Queue

A queue is a first-in, first-out data structure. Items Pushed are inserted at the rear, or 'tail' of the queue. Items removed, or Popped are taken from the 'front' of the queue.

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Declaring a queue

/declare q queue

The type name is case sensitive. That is, queue will work, but Queue, QUEUE or any other permutation will not create the type.

Methods

Name	Arguments	Returns	Comments
Count	None	Integer	Number of items inserted onto the queue.
Push	String	Bool	True if the item was pushed successfully.
Pop	None	String	False is returned if IsEmpty is true.
IsEmpty	None	Bool	True if Count = 0, False otherwise.
Peek	None	String	False is returned if IsEmpty is true.

Example usage

Sub QueueTest
    /declare q queue

    /echo 'Starting Queue Test'
    /echo 'Queue is Empty: ${q.IsEmpty}'
    
    | Push entries on the queue and pop them off.
    | Note: entries are inserted (Pushed) in and removed
    | (Popped) in the same order. That is, Pushing A, B, C, D, E
    | and then Popping them will return A, B, C, D, E.
    /echo 'Pushing items onto the Queue.'

    /if (!${q.Push[A]}) {
    	/echo 'Queue Push of A failed.'
	/endmacro
    }
    /if (!${q.Push[B]}) {
    	/echo 'Queue Push of B failed.'
	/endmacro
    }
    /if (!${q.Push[C]}) {
    	/echo 'Queue Push of C failed.'
	/endmacro
    }
    /if (!${q.Push[D]}) {
    	/echo 'Queue Push of D failed.'
	/endmacro
    }
    /if (!${q.Push[E]}) {
    	/echo 'Queue Push of E failed.'
	/endmacro
    }

    /declare count int
    /varset count ${q.Count}
    /if (${count} != 5) {
    	/echo 'Queue count is: ${count} and should be 5.'
	/endmacro
    }

    /echo 'Queue is Empty: ${q.IsEmpty}'
    
    | Peek at the front item:
    /echo 'Front item is: ${q.Peek}'
    
    | Pop items off the queue.

    /echo 'Popping item off queue: ${q.Pop}'
    /echo 'Popping item off queue: ${q.Pop}'
    /echo 'Popping item off queue: ${q.Pop}'
    /echo 'Popping item off queue: ${q.Pop}'
    /echo 'Popping item off queue: ${q.Pop}'

    /echo 'Queue is Empty: ${q.IsEmpty}'
    /echo 'Ending Queue Test'
    
    /return

Notes

• Pop decreases Count by 1 unless IsEmpty is true.
• Push increases Count by 1. IsEmpty will never be true after calling Push.
• Peek retrieves the oldest element Pushed onto the queue. Count is not modified by calling Peek.