Pointer array parameter passing, pointer parameter passing

Catalog

Array parameters

One dimensional array

Two dimensional array

The pointer passes the parameter

First level pointer

The secondary pointer

A special secondary pointer

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Array parameters

One dimensional array

When we pass in a one-dimensional array, we enter the array name , The array name is a pointer to the first element

When receiving the function , Just make sure that the type of the incoming address is the same

#include<stdio.h>

void test(int arr[]) {}      //int arr[]  Can be seen as int *arr
void test1(int arr[10]){}    // What is passed in is the address pointing to the first element , and [] Independent of the value in 
void test2(int* arr){}       // One int* Pointer to type 

int main(void) {
	int arr[10] = { 0 };
	test(arr);           // take arr As a pointer , Point to first element , The type is int*
	test1(arr);  
	test2(arr);

	return 0;
}

Two dimensional array

When we pass in a two-dimensional array, we also enter the array name , The array name is an address that points to the first element , But here, the first element is regarded as a one-dimensional array

int arr[3][5] = { 
		{1,2,3,4,5}, // First element    arr It represents the address of the one-dimensional array 
		{2,3,4,5,6}, // The second element 
		{3,4,5,6,7}  // The third element 
	};

Same will arr As a pointer , Is a pointer to an array , That is, array pointers , The type is int(*)[5].

When receiving the function , Just make sure that the type of the incoming address is the same

#include<stdio.h>

void test(int arr[3][5]) {}     //int arr[][5]  Can be seen as int(*)[5]
void test1(int arr[][5]) {}    // What is passed in is to point to the first element （ Array ） The address of , And the first [] Independent of the value in 
void test2(int(*arr)[5]) {} 

                            //*arr=arr[0],*(arr+i)=arr[i]						
                            //*(arr[i]+j)=arr[i][j]
                            //*(*(arr+i)+j)=arr[i][j]  						
                            // About [] The function of array pointer can be seen in the previous article 

int main(void) {
	int arr[3][5] = { 
		{1,2,3,4,5},         // First element    arr It represents the address of the one-dimensional array 
		{2,3,4,5,6},         // The second element 
		{3,4,5,6,7}          // The third element 
	};
	test(arr);              // take arr As a pointer , Point to first element ( Array ), The type is int(*)[5]
	test1(arr);  
	test2(arr);

	return 0;
}

The pointer passes the parameter

First level pointer

When the first level pointer is passed into the function, it is passed to the address , That's the pointer , When receiving, as long as the type is the same .

#include<stdio.h>

void test(int* p) {}   // Both int* Pointer to type 
void test1(int p[]) {}

void test2(char* p) {} // Both char* Pointer to type 
void test3(char p[]) {}


int main(void) {
	int a = 10;
	int* p = &a;
	test(p);
	test1(&a);


	char b = 'w';
	char* p1 = &b;
	test2(p1);  
	test3(&b);

	return 0;
}

The secondary pointer

The function receives a second level pointer , The parameter type is a secondary pointer , As long as it is the address of the element up two levels .

void test(int** p) {}  //int** type 

	int a = 0;
	int* p = &a;
	int** p1 = &p;

	test(&p);   // Two levels down the pointer is an element or null 
	test(p1);

A special secondary pointer

I mentioned it in the array pointer before , The array pointer can be regarded as a special secondary pointer , The values of the second level and the first level are the same .

#include<stdio.h>

void test(int** p) {}  
void test1(int(*p)[]){}  // there 10 Normal should add , In order to demonstrate the secondary pointer feature, there is no 

int main(void) {

	int arr[10] = { 0 };
	int(*p)[10] = &arr;

	test(&arr);
	test(p);

	test1(&arr);
	test1(p);

	return 0;
}