Queue/Definition: Difference between revisions

=={{header|Action!}}==

===Static memory===

Following solution uses fixed array as a buffer for the queue.

<lang Action!>DEFINE MAXSIZE="200"

BYTE ARRAY queue(MAXSIZE)

BYTE queueFront=[0],queueRear=[0]

BYTE FUNC IsEmpty()

IF queueFront=queueRear THEN

RETURN (1)

FI

RETURN (0)

PROC Push(BYTE v)

BYTE rear

rear=queueRear+1

IF rear=MAXSIZE THEN

rear=0

FI

IF rear=queueFront THEN

PrintE("Error: queue is full!")

Break()

FI

queue(queueRear)=v

queueRear=rear

RETURN

BYTE FUNC Pop()

BYTE v

IF IsEmpty() THEN

PrintE("Error: queue is empty!")

Break()

FI

v=queue(queueFront)

queueFront==+1

IF queueFront=MAXSIZE THEN

queueFront=0

FI

RETURN (v)

PROC TestIsEmpty()

IF IsEmpty() THEN

PrintE("Queue is empty")

ELSE

PrintE("Queue is not empty")

FI

RETURN

PROC TestPush(BYTE v)

PrintF("Push: %B%E",v)

Push(v)

RETURN

PROC TestPop()

BYTE v

Print("Pop: ")

v=Pop()

PrintBE(v)

RETURN

PROC Main()

TestIsEmpty()

TestPush(10)

TestIsEmpty()

TestPush(31)

TestPop()

TestIsEmpty()

TestPush(5)

TestPop()

TestPop()

TestPop()

RETURN</lang>

===Dynamic memory===

Following solution uses module for dynamic memory allocation. The user must type in the monitor the following command after compilation and before running the program!<pre>SET EndProg=*</pre>

<lang Action!>CARD EndProg ;required for ALLOCATE.ACT

INCLUDE "D2:ALLOCATE.ACT" ;from the Action! Tool Kit. You must type 'SET EndProg=*' from the monitor after compiling, but before running this program!

DEFINE PTR="CARD"

DEFINE NODE_SIZE="3"

TYPE QueueNode=[BYTE data PTR nxt]

QueueNode POINTER queueFront,queueRear

BYTE FUNC IsEmpty()

IF queueFront=0 THEN

RETURN (1)

FI

RETURN (0)

PROC Push(BYTE v)

QueueNode POINTER node

node=Alloc(NODE_SIZE)

node.data=v

node.nxt=0

IF IsEmpty() THEN

queueFront=node

ELSE

queueRear.nxt=node

FI

queueRear=node

RETURN

BYTE FUNC Pop()

QueueNode POINTER node

BYTE v

IF IsEmpty() THEN

PrintE("Error: queue is empty!")

Break()

FI

node=queueFront

v=node.data

queueFront=node.nxt

Free(node,NODE_SIZE)

RETURN (v)

PROC TestIsEmpty()

IF IsEmpty() THEN

PrintE("Queue is empty")

ELSE

PrintE("Queue is not empty")

FI

RETURN

PROC TestPush(BYTE v)

PrintF("Push: %B%E",v)

Push(v)

RETURN

PROC TestPop()

BYTE v

Print("Pop: ")

v=Pop()

PrintBE(v)

RETURN

PROC Main()

AllocInit(0)

queueFront=0

queueRear=0

Put(125) PutE() ;clear screen

TestIsEmpty()

TestPush(10)

TestIsEmpty()

TestPush(31)

TestPop()

TestIsEmpty()

TestPush(5)

TestPop()

TestPop()

TestPop()

RETURN</lang>

{{out}}

Error at the end of the program is intentional.

[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Queue_array.png Screenshot from Atari 8-bit computer]

<pre>

Queue is empty

Push: 10

Queue is not empty

Push: 31

Pop: 10

Queue is not empty

Push: 5

Pop: 31

Pop: 5

Pop: Error: queue is empty!

RETURN

Error: 128

</pre>