C语言
这个函数调用没有用到参数，那还传参数干什么？
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我也要 关注 + 加入社区 各位大侠， 下面这个函数中都没有用到参数，那还设置参数干什么？代码分为三个部分，一个.h文件，两个.c文件。
Listing 17.3. The list.h Interface Header File
Listing 17.4. The films3.c Program
Listing 17.5. The list.c Implementation File
谢谢指教！
Listing 17.3. The list.h Interface Header File
/* 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;
/* 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
Listing 17.4. The films3.c Program
/* films3.c -- using an ADT-style linked list */
/* compile with list.c */
#include <stdio.h>
#include <stdlib.h> /* prototype for exit() */
#include "list.h" /* defines List, Item */
void showmovies(Item item);
int main(void)
{
List movies;
Item temp;
/* initialize */
InitializeList(&movies);
if (ListIsFull(&movies))
{
fprintf(stderr,"No memory available! Bye!\n");
exit(1);
}
/* gather and store */
puts("Enter first movie title:");
while (gets(temp.title) != NULL && temp.title[0] != '\0')
{
puts("Enter your rating <0-10>:");
scanf("%d", &temp.rating);
while(getchar() != '\n')
continue;
if (AddItem(temp, &movies)==false)
{
fprintf(stderr,"Problem allocating memory\n");
break;
}
if (ListIsFull(&movies))
{
puts("The list is now full.");
break;
}
puts("Enter next movie title (empty line to stop):");
}
/* display */
if (ListIsEmpty(&movies))
printf("No data entered. ");
else
{
printf ("Here is the movie list:\n");
Traverse(&movies, showmovies);
}
printf("You entered %d movies.\n", ListItemCount(&movies));
/* clean up */
EmptyTheList(&movies);
printf("Bye!\n");
return 0;
}
void showmovies(Item item)
{
printf("Movie: %s Rating: %d\n", item.title, item.rating);
}
Listing 17.5. The list.c Implementation File
/* list.c -- functions supporting list operations */
#include <stdio.h>
#include <stdlib.h>
#include "list.h"
/* local function prototype */
static void CopyToNode(Item item, Node * pnode);
/* interface functions */
/* set the list to empty */
void InitializeList(List * plist)
{
* plist = NULL;
}
/* returns true if list is empty */
bool ListIsEmpty(const List * plist)
{
if (*plist == NULL)
return true;
else
return false;
}
/* returns true if list is full */
bool ListIsFull(const List * plist) //这个函数比较奇怪，明明参数，函数定义中却没有使用
{
Node * pt;
bool full;
pt = (Node *) malloc(sizeof(Node));
if (pt == NULL)
full = true;
else
full = false;
free(pt);
return full;
}
/* returns number of nodes */
unsigned int ListItemCount(const List * plist)
{
unsigned int count = 0;
Node * pnode = *plist; /* set to start of list */
while (pnode != NULL)
{
++count;
pnode = pnode->next; /* set to next node */
}
return count;
}
/* creates node to hold item and adds it to the end of */
/* the list pointed to by plist (slow implementation) */
bool AddItem(Item item, List * plist)
{
Node * pnew;
Node * scan = *plist;
pnew = (Node *) malloc(sizeof(Node));
if (pnew == NULL)
return false; /* quit function on failure */
CopyToNode(item, pnew);
pnew->next = NULL;
if(scan == NULL) /* empty list, so place */
*plist = pnew; /* pnew at head of list */
else
{
while (scan->next != NULL)
scan = scan->next; /* find end of list */
scan->next = pnew; /* add pnew to end */
}
return true;
}
/* visit each node and execute function pointed to by pfun */
void Traverse (const List * plist, void (* pfun)(Item item) )
{
Node * pnode = *plist; /* set to start of list */
while (pnode != NULL)
{
(*pfun)(pnode->item); /* apply function to item */
pnode = pnode->next; /* advance to next item */
}
}
/* free memory allocated by malloc() */
/* set list pointer to NULL */
void EmptyTheList(List * plist)
{
Node * psave;
while (*plist != NULL)
{
psave = (*plist)->next; /* save address of next node */
free(*plist); /* free current node */
*plist = psave; /* advance to next node */
}
}
/* local function definition */
/* copies an item into a node */
static void CopyToNode(Item item, Node * pnode)
{
pnode->item = item; /* structure copy */
}
谢谢指教！
...全文
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