typedef struct wave_info
{
     double freq;
     double amp;
     double phase;
     struct wave_info *next;
}WAVE;

#include <stdio.h>
#include <stdlib.h>

typedef struct wave_info
{
     double freq;
     double amp;
     double phase;
     struct wave_info *next;
}WAVE;

/*GLOBALS to track current and head position always*/
WAVE* 	current;
WAVE*	head;


void add_wave(WAVE* new_wave)
{

	new_wave->next = 0;
	if(head){			/*There is data in the list already*/
		if(!current)				/*Just in case current is off the list*/
			current = head;
		while(current->next)		/*Go to last position in list*/
			current= current->next;
		current->next = new_wave;   /*Set new_wave at end*/
    }
	else
		head = new_wave;			/*If no data put at head position*/

}

void del_wave()
{
	WAVE* temp;

	if(current){					/*Make sure we are pointing at something*/
		if(head = current)			/*If at the front of the list just reassing head*/
			head = head->next;
		else{
			temp = head;
			while(temp->next != current)	/*Place temp right before current*/
				temp = temp->next;
			temp->next = current->next;		/*Loop around current*/
		}
		free(current); 						/*Free memory*/
		current = head;
	}
}


void list_all()
{
	if(head){				/*Check to see if there is data*/
		current = head;		/*Goto top of list*/
		do{
			printf("Freq: %f - Amp: %f - Phase: %f\n",current->freq,current->amp,current->phase);
			current = current->next;		/*Position current to next data*/
		}while(current);	/*Loop until current points to null*/
    }

}

void list_current()
{
	if(current)
		printf("Freq: %f - Amp: %f - Phase: %f\n",current->freq,current->amp,current->phase);
}


int main()
{
	char	string[50];
	char    select;
	WAVE*	new_wave;

	head = current = 0;

	do{
		printf("Select a function: \n");
		printf("\tA - Add a wave.\n");
		printf("\tD - Delete a wave.\n");
		printf("\tH - Go to first wave.\n");
		printf("\tN - Go to next wave.\n");
		printf("\tP - Print waves.\n");
		printf("\tX - Exit Program.\n");
		printf("\nEnter Selection: ");
		fgets(string,4,stdin);
		select = toupper(string[0]);
		switch(select){
			case 'A':
				new_wave = (WAVE*) malloc(sizeof(WAVE));
                printf("Enter Frequency: ");
				fgets(string,49,stdin);
				new_wave->freq = atof(string);
				printf("Enter amplitude: ");
				fgets(string,49,stdin);
				new_wave->amp = atof(string);
				printf("Enter phase: ");
				fgets(string,49,stdin);
				new_wave->phase = atof(string);
				add_wave(new_wave);
				break;
			case 'D':
				del_wave();
				break;
			case 'H':
				current = head;
				if(current){
					printf("Current Wave is:\n");
					list_current();
				}
				break;
			case 'N':
				if(current){
					if(current->next)
						current = current->next;
					printf("Current Wave is:\n");
				}
				list_current();
				break;
			case 'P':
				list_all();
				break;
			case 'X':
				break;
			default:
				printf("\n\nERROR - Unknown command.\n\n");
				break;
		}
	}while(select != 'X');

	return(0);
}

void del_wave()
{
  WAVE* temp;

  if(current){          /*Make sure we are pointing at something*/
    if(head = current)      /*If at the front of the list just reassing head*/
      head = head->next;

void del_wave()
{
  WAVE* temp;

  if(current){          /*Make sure we are pointing at something*/
    if(head == current)      /*If at the front of the list just reassing head*/
      head = head->next;