feat(c++): reference syntax example

.gitignore

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+**/output/**

README.md

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-# examples
+# Examples
+
+기술 블로그 작성 등에 쓰인 예시 코드들 모음

c++/cpp-reference-syntax/ex1.cpp

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+#include <iostream>
+using namespace std;
+
+int main(void)
+{
+    int num=100;
+    int &ref=num;
+
+    cout<<"num: "<<&num<<endl;
+    cout<<"ref: "<<&ref<<endl;
+    // num: 0x16b3dec38
+    // ref: 0x16b3dec38
+
+    num=200;
+    cout<<"val: "<<num<<endl;
+    cout<<"ref: "<<ref<<endl;
+    // val: 200
+    // ref: 200
+
+    ref=300;
+    cout<<"val: "<<num<<endl;
+    cout<<"ref: "<<ref<<endl;
+    // val: 300
+    // ref: 300
+    return 0;
+}

c++/cpp-reference-syntax/ex2.cpp

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+#include <iostream>
+using namespace std;
+
+int main(void)
+{
+    int *ptr=new int;
+    int &ref=*ptr;
+    ref=20;
+    cout<<"ref: "<<ref<<endl;
+    cout<<"*ptr: "<<*ptr<<endl;
+    return 0;
+}

c++/cpp-reference-syntax/ex3.cpp

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+#include <iostream>
+using namespace std;
+
+int main(void)
+{
+    int num1=100;
+    int &num2=num1;
+    int &num3=num1;
+    int &num4=num3;
+
+    cout<<"num1: "<<num1<<endl;
+    cout<<"num2: "<<num2<<endl;
+    cout<<"num3: "<<num3<<endl;
+    cout<<"num4: "<<num4<<endl;
+    // num1: 100
+    // num2: 100
+    // num3: 100
+    // num4: 100
+
+    // int &ref;
+    // int &ref=NULL;
+
+    int arr[3]={1, 3, 5};
+    int &first=arr[0];
+    int &second=arr[1];
+    int &third=arr[2];
+
+    cout<<"first: "<<first<<endl;
+    cout<<"second: "<<second<<endl;
+    cout<<"third: "<<third<<endl;
+    // first: 1
+    // second: 3
+    // third: 5
+
+    int num=10;
+    int *ptr=&num;
+    int *(&ptrRef)=ptr;
+
+    cout<<"ptr: "<<*ptr<<endl;
+    cout<<"ptrRef: "<<*ptrRef<<endl;
+
+    return 0;
+}

c++/cpp-reference-syntax/ex4.cpp

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+#include <iostream>
+using namespace std;
+
+int main(void)
+{
+    // int &ref=20; // 컴파일 실패
+    const int &ref=20;
+
+    const int num=100;
+    const int &ref1=num;
+    const int &ref2=100;
+
+    // const int num=100;
+    // const int &ref=num;
+
+    // const int num=100;
+    // int &ref=num; // 컴파일 실패
+    // ref+=10;
+    // cout<<"num1: "<<num<<endl;
+
+    // int &num3=num1;
+    // int &num4=num3;
+    return 0;
+}

c++/cpp-reference-syntax/ex5.cpp

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+#include <iostream>
+using namespace std;
+
+// int SwapByVal(int num1, int num2)
+// {
+//     int temp=num1;
+//     num1=num2;
+//     num2=temp;
+// }
+
+// int SwapByPtr(int * ptr1, int * ptr2)
+// {
+//     int temp=*ptr1;
+//     *ptr1=*ptr2;
+//     *ptr2=temp;
+// }
+
+int SwapByRef(int &ref1, int &ref2)
+{
+    int temp=ref1;
+    ref1=ref2;
+    ref2=temp;
+}
+
+int main(void)
+{
+    int val1=10;
+    int val2=20;
+    SwapByRef(&val1, &val2);
+    cout<<"val1: "<<val1<<endl;
+    cout<<"val2: "<<val2<<endl;
+    // val1: 20
+    // val2: 10
+    return 0;
+}

c++/cpp-reference-syntax/ex6.cpp

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+#include <iostream>
+using namespace std;
+
+int Do(int &ref)
+{
+    ref++;
+}
+
+int Func(const int &ref)
+{
+    // ref=1; // 컴파일 에러
+}
+
+int main(void)
+{
+    int num=1;
+    Do(num);
+    cout<<num<<endl;
+    return 0;
+}

c++/cpp-reference-syntax/ex7.cpp

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+#include <iostream>
+using namespace std;
+
+int& RefReturnFunc(int &ref)
+{
+    ref++;
+    return ref;
+}
+
+int Func(int &ref)
+{
+    ref++;
+    return ref;
+}
+
+int main(void)
+{
+    // int num1=1;
+    // int num2=RefReturnFunc(num1);
+
+    // num1+=10;
+    // num2+=100;
+    // cout<<"num1: "<<num1<<endl;
+    // cout<<"num2: "<<num2<<endl;
+    // // num1: 12
+    // // num2: 102
+    // cout<<"num1: "<<&num1<<endl;
+    // cout<<"num2: "<<&num2<<endl;
+    // // num1: 0x16f9f2c38
+    // // num2: 0x16f9f2c34
+
+
+    int num1=1;
+    int num2=RefReturnFunc(num1);
+    int &num3=RefReturnFunc(num1);
+    int num4=Func(num1);
+    // int &num5=Func(num1); // 컴파일 에러
+
+    cout<<"num1: "<<&num1<<endl;
+    cout<<"num2: "<<&num2<<endl;
+    cout<<"num3: "<<&num3<<endl;
+    cout<<"num4: "<<&num4<<endl;
+    return 0;
+}

c++/cpp-reference-syntax/ex8.cpp

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+#include <iostream>
+using namespace std;
+
+int& RefReturnFunc()
+{
+    int num=20;
+    num+=10;
+    return num;
+}
+
+int main(void)
+{
+    int num=RefReturnFunc();
+    cout<<"num: "<<endl;
+    cout<<"num: "<<endl;
+    cout<<"num: "<<endl;
+    cout<<"num: "<<num<<endl;
+    return 0;
+}