新手求助：C Primer Plus书中高级数据一章中抽象数据类型（ADT）的问题

qq_30355845 2015-08-04 04:04:37

/* list.h -- header file for a simple list type */

#ifndef LIST_H_

#define LIST_H_

#include <stdbool.h> /* C99 feature */

/* program-specific declarations */

#define TSIZE 45 /* size of array to hold title */

struct film

{

char title[TSIZE];

int rating;

};

/* general type definitions */

typedef struct film Item;

typedef struct node

{

Item item;

struct node * next;

} Node;

typedef Node * List; //这里把一个结构体 Node 定义成一个指针 * List，不是很明白，请具体讲解一下，谢谢！

/* function prototypes */

/* operation: initialize a list */

/* preconditions: plist points to a list */

/* postconditions: the list is initialized to empty */

void InitializeList(List * plist);

/* operation: determine if list is empty */

/* plist points to an initialized list */

/* postconditions: function returns True if list is empty */

/* and returns False otherwise */

bool ListIsEmpty(const List *plist);

/* operation: determine if list is full */

/* plist points to an initialized list */

/* postconditions: function returns True if list is full */

/* and returns False otherwise */

bool ListIsFull(const List *plist);

/* operation: determine number of items in list */

/* plist points to an initialized list */

/* postconditions: function returns number of items in list */

unsigned int ListItemCount(const List *plist);

/* operation: add item to end of list */

/* preconditions: item is an item to be added to list */

/* plist points to an initialized list */

/* postconditions: if possible, function adds item to end */

/* of list and returns True; otherwise the */

/* function returns False */

bool AddItem(Item item, List * plist);

/* operation: apply a function to each item in list */

/* plist points to an initialized list */

/* pfun points to a function that takes an */

/* Item argument and has no return value */

/* postcondition: the function pointed to by pfun is */

/* executed once for each item in the list */

void Traverse (const List *plist, void (* pfun)(Item item) );

/* operation: free allocated memory, if any */

/* plist points to an initialized list */

/* postconditions: any memory allocated for the list is freed */

/* and the list is set to empty */

void EmptyTheList(List * plist);

#endif

根据 typedef Node * List 这个定义， List实际上就是个 Node结构体的指针了是吗？但是我在后面的代码中又看到了这样的变量声明和函数参数传递。 List movies; InitializeList(&movies); 既然根据前面的typedef定义List本来就是一个指针了，也就是说变量movies本身就是个Node结构体指针。那么，为何把它当做函数参数传递时还要用&movies的形式呢？谢谢！

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