a simple linked list

header file:

#ifndef LINKLIST_H_INCLUDED
#define LINKLIST_H_INCLUDED

struct node;
typedef struct node mynode;
typedef struct node *ptr_to_node;
typedef ptr_to_node list;
typedef ptr_to_node position;

list create_empty(void);
int is_empty(list l);
int is_last(position p,list l);
position find(char x,list l);
void delete_element(char x,list l);
void delete_position(position p,list l);
position find_previous(char x,list l);
void insert_after(char x,list l,position p);
void insert_before(char x,list l,position p);
void delete_list(list l);
position get_header(list l);
position get_first(list l);
char get_value(position p);

#endif // LINKLIST_H_INCLUDED

implement file:

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

struct node
{
    char value;
    ptr_to_node next;
};

int is_empty(list l)
{
    return l->next==NULL;
}

list create_empty(void)
{
    return (list)malloc(sizeof(mynode));
}

int is_last(position p,list l)
{
    return p->next==NULL;
}

position get_first(list l)
{
    return l->next;
}

position get_header(list l)
{
    return l;
}

char get_value(position p)
{
    return p->value;
}

position find(char x,list l)
{
    position p=l->next;
    while(p!=NULL)
    {
        if(p->value==x)
        {
            return p;
        }
        p=p->next;
    }

    return NULL;
}

position find_previous(char x,list l)
{
    position p=l;
    while(p!=NULL && p->next!=NULL)
    {
        if(p->next->value==x)
        {
            return p;
        }
        p=p->next;
    }

    return NULL;
}

position find_previous2(position p,list l)
{
     position c=l;
     while(c!=NULL && c->next!=p)
     {
         c=c->next;
     }
     return c;
}

void insert_after(char x,list l,position p)
{
    ptr_to_node t=create_empty();
    t->value=x;
    position oldnext=p->next;
    t->next=oldnext;
    p->next=t;
}

void insert_before(char x,list l,position p)
{
    position previous=find_previous2(p,l);
    if(previous==NULL)
    {
        return;
    }

    insert_after(x,l,previous);
}

void delete_element(char x,list l)
{
    position current=find(x,l);
    if(current==NULL)
    {
        return;
    }
    position previous=find_previous(x,l);
    previous->next=current->next;
    free(current);
}

void delete_position(position p,list l)
{
    position previous=find_previous2(p,l);
    previous->next=p->next;
    free(p);
}

void delete_list(list l)
{
    position p=l->next;
    position t;
    while(p!=NULL)
    {
        t=p->next;
        free(p);
        p=t;
    }
    //RESET THE HEADER
    l->next=NULL;
}

void print_list(list l)
{
    position p;
    p=l;
    while(p!=NULL)
    {
        printf("%c,",p->value);
        p=p->next;
    }
    printf("\n");
}

main:

int main()
{
    int i;
    position p;
    list l=create_empty();
    l->value='%';
    l->next=NULL;
    for(i=65;i<91;i++)
    {
        insert_after(i,l,l);
    }

    print_list(l);

    p=find('B',l);
    if(p!=NULL)
    {
        printf("B after is:%c\n",p->next->value);
    }

    delete_element('C',l);
    print_list(l);

    p=find('B',l);
    insert_before('C',l,p);
    print_list(l);

    delete_position(p,l);
    print_list(l);

    p=find('X',l);
    if(p!=NULL)
    {
        printf("found X:%c\n",p->value);
    }
    p=find_previous2(p,l);
    if(p!=NULL)
    {
        printf("X before is:%c\n",p->value);
    }
    delete_list(l);
    print_list(l);
    return 0;
}