(Basic) C + + syntax _1

I think the comments are detailed, haha.

<pre name= "code" class= "CPP" >//namespaces use example. cpp #include <iostream>using namespace std; Space STD covers all standard C + + definitions and declarations namespace one//defines a namespace one with 1 constants m and a variable inf {const int m = 200;int inf = 10;}//followed by no semicolon  names Pace two//defines a namespace two with two variables {int x;int inf =-100;}  

The domain resolver really has global scope for global variables. cpp #include <iostream> #include <iomanip>//? Using namespace Std;intsum = 5000;//defines the global variable Sumint main () {int arr[3] = {10, 20, 30};//a small program block starts with {int i, sum = 0;for (int i = 0 ; I < 3; i++) {sum + = Arr[i];} cout<< "Local sum:" <<sum<<endl;//output local sum:: Sum + = sum;//through the domain resolver to global sum access in the scope of the local variable with the same name cout<< " Global sum: "<<::sum<<endl;} Sum *= 2;//This is the global sumcout<< "total sum:" <<::sum<<endl;int sum = 200;//define another sumcout<< "Local sum:" <<sum<<endl;::sum + = sum;//10120 + cout<< "Global sum:" <<::sum<<endl;return 0;  

Formal parameters function definitions with default parameter values and invocation examples. cpp #include <iostream>using namespace std;void fun (int i, int j = 5, int k = 10);//prototype declaration of parameter J and k Specify the default parameters 5 and 10int respectively main () {fun (20); Fun (14, 30); Fun (0); }  void Fun (int i, int j, int k)//is defined in the prototype, can no longer be specified in the defined header {cout<<i<< "" <<j<< "" <<k<< Endl;}

Two-number multiplication (wrong) is achieved by using a macro definition. cpp #include <iostream>using namespace std; #define MULTIPLY (x, y) x*y//Note: There are no parentheses on either side of X and Y, there is a hidden danger int Main () {int a = Multiply (3 + 4, 2 + 3);//expanded to: int a = 3 + 4*2 + 3cout<< "a =" <<a<<endl;//output 14, original plan is 7*5 = return 0;  

//two-number multiplication with inline functions. cpp #include <iostream>using namespace Std;inline int Multiply (int x, int y)//In Object-oriented programming, the member functions defined in the class are automatically interpreted as inline functions, re Turn x * y;//no need to add the inline keyword}int main () {int a = Multiply (3 + 4, 2 + 3), cout << "a =" << a << endl;//used After the inline function, it really avoids the macro definition of that error, the return 0;//output value is ' {} ' 

Examples of overloaded functions. CPP//In the C + + language, for the function is exactly the same or similar, just the number of formal parameters,//type, the order of different functions with the same function name to name,//the same name function is collectively referred to as overloading (overload) #include < Iostream>using namespace Std; int square (int x)//The 1th version of the overloaded function, int type parameter {return x * x;}  float square (float x)//2 version {return x * x;} Double square (Double x = 1.5)//3 Version {return x * x;} int main () {cout << "square () =" << square () << endl;//calls the third version because it has a default value of cout << "square" = "&l t;< Square << endl;//call the first version cout << "Square (2.5f) =" << Square (2.5f) << Endl;//2editioncou T << "Square (1.1) =" << Square (1.1) << Endl;return 0;}

(Basic) C + + syntax _1