C数组指针函数指针做函数参数和返回值

　　数组和函数不能用做参数和返回值，但数组指针和函数指针可以。
　　1 数组指针做函数参数
　　数组指针做函数参数，数组名用做实参时，其形参为指向数组首元素的指针（指针目标类型为数组元素）。#include  #include  #define ROWS 3 #define COLS 2 void fun1(int (*)[COLS], int); int main() {     int array_2D[ROWS][COLS] = { {1, 2}, {3, 4}, {5, 6} };     int rows = ROWS;     /* works here because array_2d is still in scope and still an array */     printf(＂MAIN: %zu ＂,sizeof(array_2D)/sizeof(array_2D[0]));     fun1(array_2D, rows);     getchar();     return EXIT_SUCCESS; } void fun1(int (*a)[COLS], int rows) {     int i, j;     int n, m;     n = rows;     /* Works, because that information is passed (as ＂COLS＂).     It is also redundant because that value is known at compile time (in ＂COLS＂). */     m = (int) (sizeof(a[0])/sizeof(a[0][0]));     /* Does not work here because the ＂decay＂ in ＂pointer decay＂ is meant     literally--information is lost. */     printf(＂FUN1: %zu ＂,sizeof(a)/sizeof(a[0]));     for (i = 0; i < n; i++) {         for (j = 0; j < m; j++) {             printf(＂array[%d][%d]=%d ＂, i, j, a[i][j]);         }     } }
　　2 数组指针做函数返回值
　　数组指针做函数返回值时，数组指针是指指针目标类型为数组元素的指针。#include  #include   char(*weekday())[5] {     char(*wee)[5] = (char(*)[5])malloc(sizeof(char)*5*7);     char* str[] = {＂Mon.＂,＂Tue＂,＂Wed.＂,＂Thu.＂,＂Fri.＂,＂Sat.＂,＂Sun.＂};     for(int i=0;i<7;i++)         for(int j=0;j<5;j++)             wee[i][j] = str[i][j];     return wee; }  int main() {     char(*week)[5] = weekday();     for(int i=0;i<7;i++)         printf(＂%s ＂,week[i]);     free(week);     setbuf(stdin,NULL);     getchar(); }
　　3 函数指针做函数参数
　　函数指针做函数参数，可以封装函数体中因因应不同需求而需＂变化＂的代码，避免＂硬＂编程，让代码更加通用和泛化。#include  void sort(int arr[],int size,bool(*comp)(int,int)) {     for(int i=0;i  enum Op {     ADD = ＂+＂,     SUB = ＂-＂, };  int add(int a, int b) {     return a + b; }  int sub(int a, int b) {     return a - b; } /* getmath: return the appropriate math function */ int (*getmath(enum Op op))(int,int) {     switch (op)     {     case ADD:         return &add;     case SUB:         return       default:         return NULL;     } }  int main(void) {     int a, b, c;     int (*fp)(int,int);     fp = getmath(ADD);     a = 1, b = 2;     c = (*fp)(a, b);     printf(＂%d + %d = %d ＂, a, b, c);     getchar();     return 0; }
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