# C++
## 安裝
1. Dev-C++ [link](https://sourceforge.net/projects/orwelldevcpp/)
2. vscode [link](https://code.visualstudio.com/download)
## 特性
1. 編譯
2. 物件導向
## 變數
| 類型 | 空間 | range |
| ------------- | ---------------- | ------------------------ |
| bool | 1 bit | (0 to 1 )or (true to false) |
| int | 2 Bytes(2*8 bit) | -2^15 to 2^15-1 |
| long int | 4 Bytes(4*8 bit) | -2^23 to 2^23-1 |
| long long int | 8 Bytes(4*8 bit) | -2^31 to 2^31-1 |
| float | 4 Bytes(4*8 bit) | |
| doblue | 8 Bytes(8*8 bit) | |
### int
```c++
#include <stdio.h>
int main()
{
int var_name;
int w2,ww;
var_name=4;
w2=1;
ww=42342;
}
```
### float
```c++
float test=10;
float var= 0.003;
```
### double
```c++
double test=10;
double var= 0.003;
```
### 陣列(array)
```c++
//宣告
int mo={0,1,2,3};
int num[4],mo[4];
float num[4],mo[4];
double num[4],mo[4];
char num[4],mo[4];
//儲存資料
mo[0]=0;
mo[1]=1;
mo[2]=2;
mo[3]=3;
//讀取資料
printf("%.3f", mo[3]);
```
## 輸入 輸出
### printf
```c++
//int
printf("%d",a);
//float or double
printf("%lf",a);
//string
printf("%s",a);
//輸出
//特殊字元
//換行
printf("\n");
//tab
printf("\t");
//\
printf("\\");
```
### scanf
```c++
int a;
scanf("%d",&a);
float b;
scanf("%lf",&b);
char c[] = "some text";
scanf("%s",&c);
```
## if
```c++
//判別式
a<b
a>b
a==b
int a ,b;
a=2;
b=3;
if(a>b)
{
printf("%d big", a);
}
else
{
printf("%d big", b);
}
```
## 迴圈
### for
```c++
#include <stdio.h>
int main()
{
int i;
for (i = 0; i < 100; i++)
{
printf("%d\n", i);
}
}
```
### while
```c++
#include <stdio.h>
int main()
{
int i=0;
while(i<10)
{
printf("%d\n", i);
i=i+1;
}
return 0;
}
```
## function
### return
```c++
int test_function(int a,int b)
{
int var;
var=a*b;
return var;
}
int something = test_function(4,8)
```
### void
```c++
void test(int a)
{
printf("%d",a);
}
int main()
{
int var;
var = 12;
test(var);
return 0;
}
```
### call by value
```c++
void test(int a)
{
printf("a1 %d\n", a);
a = 10;
printf("a2 %d\n", a);
//10
}
int main()
{
int var = 8;
printf("va1 %d\n", var);
test(var);
printf("va2 %d\n", var);
return 0;
}
//8
```
### call by reference
```c++
void test(int &a)
{
printf("a1 %d\n", a);
a = 10;
printf("a2 %d\n", a);
//10
}
int main()
{
int var = 8;
printf("va1 %d\n", var);
test(var);
printf("va2 %d\n", var);
return 0;
}
//10
```
### call by address
```cpp
void test(int* a)
{
printf("a1 %d\n", a);
printf("a1_v %d\n", *a);
*a = 10;
printf("a2 %d\n", a);
printf("a2_v %d\n", *a);
}
int main()
{
int var = 8;
printf("va1 %d\n", var);
test(&var);
printf("va2 %d\n", var);
return 0;
}
//10
```
## class (物件導向)
### basic
public 可以讀取
private 不可讀取
```c++
class test {
public:
int a=10;
int b;
int DoSomething();
void printf(int a)
{
printf("%d",test::a);
}
private:
int size;
string color;
};
int test::DoSomething() {
return a + b;
}
int main(){
test d;
printf("%d",d.a);
}
```
### constructor,destructor
```cpp
class test {
public:
int m_a=10;
int m_b;
int DoSomething();
//constructer
test(){
m_a=0;
m_b=1;
}
//constructer
//initialize list: constructerwill initialize child var before constructer
test(int a,int b):m_a(a),m_b(b){}
//destructor
~test(){
//destructor will call when the var is going to be remove
delete m_a;
delete m_b;
}
}
int main(){
test d1();
test d2;
printf("%d",d1.a);
}
```
### copy constructer
```cpp
class test {
public:
int m_a=10;
int m_b;
//call when the another need copy of the value
test(const test &set_test){
this->m_a=set_test.m_a;
this->m_b=set_test.m_b;
}
}
int main(){
test d1(1,2);
test d2=d2;
printf("%d",d2.a);
}
```
### copy assignment
```cpp
class test {
public:
int m_a=10;
int m_b;
//call when var need to be overwrite by another var
//so need to free the child var
//"conset" mean this funciton will not change the input argement var
//"&test mean" return the reference of the var
//"&set_test" mean input the reference of the var
&test operator =(const test &set_test){
delete this->m_a;
delete this->m_b;
this->m_a=set_test.m_a;
this->m_b=set_test.m_b;
return *this
}
}
int main(){
test d1(1,2);
test d2(3,4);
d1=d2;
printf("%d",d1.a);
}
```
## 惡夢開始
### ::的意義
#### 全域變數
```cpp
int tem=0;
void main(){
::tem=::tem+10;
}
```
#### 和外定義class的資料
```cpp
class test {
public:
int a=10;
int b;
int something();
};
int test::something(){
printf(this->a);
}
```
#### .
```cpp
System::Math::Sqrt()=System.Math.Sqrt()
```
### this
```cpp
class test {
public:
int a=10;
int b;
int something();
};
int test::something(){
printf(this->a);
}
```
### ->
```cpp
struct a{
int v=10;
int b;
};
int something(a *a_ptr){
printf(a_ptr->v);
printf(*(a_ptr).v);
}
```
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