// learn with examples @ 2020
// onecompiler.com/cpp/435h87umn

// 1. Default (zero-parameter) constructor: no arguments
// 2. Parameterized constructor: accepting parameters
// 3. Converting constructor: any non-explicit parameterized constructor (since C++11)
// 4. Copy constructor of class T: T([const] [volatile] T&), called when:
//   a) initialization: T a = b; or T a(b);, where b is of type T;
//   b) function argument passing: f(a);, where a is of type T and f is void f(T t);
// 5. Move constructor of class T: T([const] [volatile] T&&), called when:
//   a) initialization: T a = std::move(b); or T a(std::move(b));, where b is of type T;
//   b) function argument passing: f(std::move(a));, where a is of type T and f is f(T t);
// note: because of Return Value Optimization (RVO), most compilers don't invoke copy/move constructor when returning an object such as T f() {return T a;}.
#include <iostream>
#include <string>
using namespace std;

class  MyClass {
public:
  int x;
  MyClass() {
    cout << "Default (zero-parameter) constructor called via MyClass newObj" << endl;
    x = 0;
  }
  explicit MyClass(int x) {
    cout << "Parameterized constructor called via: MyClass newObj(x)" << endl;
    this->x = x;
  }
  MyClass(double x) {
    cout << "Converting constructor called via: MyClass newObj = x;" << endl;
    this->x = (int)x;
  }
  MyClass(const MyClass& m) {
    cout << "Copy constructor called via: MyClass newObj = m, MyClass newObj(m), or MyFunc(m)" << endl;
    this->x = m.x;
  }
  MyClass(MyClass&& m) {
    cout << "Move constructor called via: MyClass newObj = move(m), or MyFunc(move(m));" << endl;
    this->x = m.x;
  }
};

void myFunc(MyClass m) {}

int main() {
  MyClass m1; // 1. Default (zero-parameter) constructor: no arguments
  MyClass m2(2); // 2. Parameterized constructor: accepting parameters
  MyClass m3 = 3.14; // 3. Converting constructor: non-explicit parameterized constructor (since C++11)
  MyClass m4_1 = m1; // 4a. Copy constructor: m1 -> m4
  MyClass m4_2(m1); // 4a. Copy constructor: m1 -> m4
  myFunc(m1); // 4b. Copy constructor, function argument passing
  MyClass m5 = move(m1); // 5a. Move constructor: m1 -> m5
  myFunc(move(m5)); // 5a. Move constructor: function argument passing
  return 0;
}
by

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Read inputs from stdin

OneCompiler's C++ online compiler supports stdin and users can give inputs to programs using the STDIN textbox under the I/O tab. Following is a sample program which takes name as input and print your name with hello.

#include <iostream>
#include <string>
using namespace std;

int main() 
{
    string name;
    cout << "Enter name:";
    getline (cin, name);
    cout << "Hello " << name;
    return 0;
}

About C++

C++ is a widely used middle-level programming language.

  • Supports different platforms like Windows, various Linux flavours, MacOS etc
  • C++ supports OOPS concepts like Inheritance, Polymorphism, Encapsulation and Abstraction.
  • Case-sensitive
  • C++ is a compiler based language
  • C++ supports structured programming language
  • C++ provides alot of inbuilt functions and also supports dynamic memory allocation.
  • Like C, C++ also allows you to play with memory using Pointers.

Syntax help

Loops

1. If-Else:

When ever you want to perform a set of operations based on a condition If-Else is used.

if(conditional-expression) {
   //code
}
else {
   //code
}

You can also use if-else for nested Ifs and If-Else-If ladder when multiple conditions are to be performed on a single variable.

2. Switch:

Switch is an alternative to If-Else-If ladder.

switch(conditional-expression){    
case value1:    
 // code    
 break;  // optional  
case value2:    
 // code    
 break;  // optional  
......    
    
default:     
 code to be executed when all the above cases are not matched;    
}

3. For:

For loop is used to iterate a set of statements based on a condition.

for(Initialization; Condition; Increment/decrement){  
  //code  
}

4. While:

While is also used to iterate a set of statements based on a condition. Usually while is preferred when number of iterations are not known in advance.

while (condition) {  
// code 
}

5. Do-While:

Do-while is also used to iterate a set of statements based on a condition. It is mostly used when you need to execute the statements atleast once.

do {  
 // code 
} while (condition);

Functions

Function is a sub-routine which contains set of statements. Usually functions are written when multiple calls are required to same set of statements which increases re-usuability and modularity. Function gets run only when it is called.

How to declare a Function:

return_type function_name(parameters);

How to call a Function:

function_name (parameters)

How to define a Function:

return_type function_name(parameters) {  
 // code
}