Lists

Recall the traditional list code snippets, as given in class:

• The list type:

       struct AList {
          int             first;
          struct AList *  rest;
       };
       typedef  struct AList *  List;
       

  My style of hiding the fact that List is pointer is based on what you're familiar with from Scheme and Java. Others prefer something like typedef struct AList Cons; In your own code, you may do what you wish.

• To create a list:

       List make_empty()
       {
          return NULL;
       }
  
       List make_cons(int first, List rest)
       {
          List  list = (List) malloc(sizeof(struct AList));
          if (list == NULL) {
             fprintf(stderr,"Out of memory.\n");
             exit(1);
          }
  
          list->first = first;
          list->rest  = rest;
          return list;
       }
       

• To access a list:

       List  list = ...;
  
       if (list == NULL) {
          ...
       }
       else {
           ...list->first ... list->rest ...
       }