#include "stdio.h"#include "stdlib.h"void func( int a[] );int main( int argc, char* argv[] ){ /* this program prove below: Except when it is the operand of the sizeof operator or the unary & operator, or is a string literal used to initialize an array, an expression that has type ‘‘array of type’’ is converted to an expression with type ‘‘pointer to type’’ that points to the initial element of the array object and is not an lvalue. -- C99 数组在除了3种情况外, 其他时候都要"退化"成指向首元素的指针. 这3中例外情况是: (1) sizeof(s) (2) &s; (3) 用来初始化s的"china"; -- C99 另外，从数组退化成的指针，不可执行++操作，即可以理解为const指针。 这里需要注意另外一点，即，函数 void func( int a[] )，在编译过程中，将参数int a[]也解释为 int * （遵循C99）， 这样，在函数内部，a++是允许的。 */ int x = 6; int * p = &x; printf("the value of point p:%d\n",*p); int y[4] = {1,2,3,4}; printf("the value of array name y:%d\n", *y); printf("the value of array name y:%d\n", *(y+1)); printf("the value of array name y:%d\n", *(y+2)); printf("the value of array name y:%d\n", *(y+3)); int * q = y; printf("the value of point q:%d\n",*q); printf("the value of point q+1:%d\n",*(++q)); printf("the value of point q+2:%d\n",*(++q)); printf("the value of point q+3:%d\n",*(++q)); /* 2D array -> 1D pointer */ int z[3][2] = {{1,2},{5,6},{9,10}}; // 数组在内存中的分配是连续的 int * r = NULL; r = (int *)&z; printf("the value of point r:%d\n",*r); printf("the value of point r+1:%d\n",*(r+1)); printf("the value of point r+2:%d\n",*(r+2)); printf("the value of point r+3:%d\n",*(r+3)); r++; printf("the value of point r:%d\n",*r); printf("the value of point r+1:%d\n",*(r+1)); printf("the value of point r+2:%d\n",*(r+2)); printf("the value of point r+3:%d\n",*(r+3)); int *s = z[0]; printf("the value of point s:%d\n",*r); printf("the value of point s+1:%d\n",*(r+1)); printf("the value of point s+2:%d\n",*(r+2)); printf("the value of point s+3:%d\n",*(r+3)); /* 2D array -> pointer of array. */ //in this segment, [x][y] is changed to pointer address plus (x-1)*y + y int (*t)[2] = (int (*)[2])z; printf("t's content: %d\n", t[0][0]); printf("t's content: %d\n", t[0][1]); printf("t's content: %d\n", t[1][0]); printf("t's content: %d\n", t[1][1]); printf("t's content: %d\n", t[0][2]); printf("t's content: %d\n", t[0][3]); printf("t's content: %d\n", t[0][4]); int (*tt)[6] = (int (*)[6])z; printf("tt's content: %d\n", tt[0][0]); // 这里把tt[0]理解为指针tt printf("tt's content: %d\n", tt[0][1]); printf("tt's content: %d\n", tt[0][2]); printf("tt's content: %d\n", tt[0][3]); printf("tt's content: %d\n", tt[0][4]); /* 1D -> pointer of array. */ int a[3] = {1,2,3}; //int *po = a; int (*poo)[3] = (int (*)[3])&a; printf("poo's content: %d\n", poo[0][0]); // 这里把poo[0]理解为指针poo printf("poo's content: %d\n", poo[0][1]); printf("poo's content: %d\n", poo[0][2]); int b[3] = {2,3,4}; func(b); printf("end\n");}void func( int a[] ){ printf(" in func, a is: %d\n", *a); printf(" in func, ++a is: %d\n", *(++a));}
