/**
  * Copyright (c): Uwe Schmidt, FH Wedel
  *
  * You may study, modify and distribute this source code
  * FOR NON-COMMERCIAL PURPOSES ONLY.
  * This copyright message has to remain unchanged.
  *
  * Note that this document is provided 'as is',
  * WITHOUT WARRANTY of any kind either expressed or implied.
  */

/*--------------------*/

/* some macros and static variables
   for making version and
   conditional compilation flags
   visible in assembler and object files
   ignore in first reading
*/

/*--------------------*/

#include "List.h"

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

/*--------------------*/

/* simple ops as functions */

List
mkEmptyList(void)
{
  return (List) 0;
}

/*--------------------*/

int
isEmptyList(List l)
{
  return l == (List) 0;
}

/*--------------------*/

Element
head(List l)
{
  assert(! isEmptyList(l));
  return l->info;
}

/*--------------------*/

List
tail(List l)
{
  assert(! isEmptyList(l));
  return l->next;
}

/*--------------------*/

List
removeHead(List l)
{
  assert(! isEmptyList(l));
  {
    List res = l->next;
    free(l);
    return res;
  }
}

List
cons(Element e, List l)
{
  /* the only call of malloc */
  List res = malloc(sizeof(*l));

  if (! res)
    {
      perror("cons: malloc failed");
      exit(1);
    }
  res->info = e;
  res->next = l;

  return res;
}

/*--------------------*/

List
addElem(Element e, List l)
{
  List *pl = &l;

  while (! isEmptyList(*pl)
         &&
         ! geElement((*pl)->info, e))
    {
      pl = &((*pl)->next);
    }

  *pl = cons(e, *pl);
  return l;
}

/*--------------------*/

/*consistency check */

int
invList(List l)
{
  if (isEmptyList(l))
    return 1;

  if (isEmptyList(l->next))
    return 1;

  return
    geElement(l->next->info, l->info)
    &&
    invList(l->next);
}

/*--------------------*/