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--- user:kkrauss1:portfolio:queue_library [2011/12/12 20:45] – kkrauss1
+++ user:kkrauss1:portfolio:queue_library [2011/12/12 20:55] (current) – [Code] kkrauss1
@@ Line 1: / Line 1: @@
+======Project: Queue Library Implementation======
+A project for C/C++, Data Structures, and System Programming  by Karl Krauss during the SEMESTER YEAR.
+I spent a few hours on this.
+=====Objectives=====
+The purpose of this project was to create a library for queues.
+=====Prerequisites=====
+In order to successfully accomplish/perform this project, the listed resources/experiences need to be consulted/achieved:
+  * understand functions
+  * understand pointers
+  * understand structs
+  * understand malloc()
+=====Background=====
+This was the next evolution of the doubly linked list and stack library.  This is the queue library, taking what I learned from implementing the dl library this was much simpler.
+=====Attributes=====
+====Cprog attributes====
+  * variables
+  * pointers
+  * selection
+  * i/o
+  * repetition
+  * functions
+  * structures
+  * libraries
+====Data Structures====
+  * Pointers
+  * Malloc/new
+  * linked list
+  * Doubly linked list
+  * Libraries
+====Systems programming====
+  * Terminal I/O
+=====Code=====
+This is the header file:
+<code c>
+#ifndef			QUEUE_H
+#define      		QUEUE_H
+struct node { //predefined structure with one variable (
+	int value;
+	struct node *next;
+	struct node *prev;
+};
+typedef struct node Node;
+struct queue {// predefined structure for use of returns in functions allow for easy access to start.  *end is end of queue start is start
+	Node *start;
+	Node *end;
+};
+typedef struct queue
+Queue;
+Queue *enqueue(Queue *myQueue, int input);
+Node *dequeue(Queue *myQueue);
+Node *peek(Queue *myQueue);
+//minimum variables needed in main: int input, Node *tmp, Node *tmp2, Queue *myList.
+#endif
+</code>
+This is the code:
+<code c>
+// This is an attempt at writing a queue library for a single variable that will include enqueue(),dequeue(), peek(),
+// printList()
+#include <stdio.h>
+#include <stdlib.h>
+#include "queue.h"
+Queue *enqueue(Queue *myQueue, int input)
+{
+	if(myQueue->start == NULL) // this is to test if the list is gempty
+	{
+		myQueue->start = (Node *)malloc(sizeof(Node));
+		myQueue->end = myQueue->start; // with only one node end and start are the same
+		myQueue->start->next = NULL; //no nodes after start(no next)
+		myQueue->start->prev = NULL; //no nodes before start(no before)
+		myQueue->start->value = input; //value is now stored in first node
+	}
+	else // list is not empty so now will will create a new node and append
+	{
+		Node *tmp = (Node *)malloc(sizeof(Node));
+		myQueue->end->next = tmp; // end's next now points to tmp instead of null, so adding a new node to end of list
+		tmp->prev = myQueue->end; //new nodes prev now points to current end
+		myQueue->end = myQueue->end->next; // moves end to the true end of the list.
+		myQueue->end->value = input; // store input into new node(end)
+		myQueue->end->next = NULL;// nothing beyond the end of the list
+	}
+	return myQueue;
+}
+Node *dequeue(Queue *myQueue)
+{
+	Node *dequeuedVal = NULL;
+	if (myQueue->start != NULL)//test if queue is empty
+	{
+		dequeuedVal = myQueue->start;// setting poppedVal equal to the current "top" of the stack
+		myQueue->start = myQueue->start->next;// changing the top of the list to the previous node
+		if(myQueue->start != NULL)
+		{
+			myQueue->start->prev = NULL;
+		}
+		/*else
+		/{
+			myStack->end->next = NULL; //disconnecting the old top from the list
+		}*/
+	}
+	return dequeuedVal;
+}
+</code>
+=====Reflection=====
+  *As with doubly linked lists,  I really learned a lot.  This library was written quite some time ago and the best part is when I came back to it, I had learned enough to realize I could vastly improve upon it. Something I will possibly do in the future.

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