C++ 11 Features and training notes

C++ 11 features

Rule of 5

-Destructor

-Copy construtor

-Copy assignment

-Move constructor

-Move assignment
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Range based for loop

for (declaration: expression){

// do some loop stuff

}

// Arrays

int arr[] = {1,2,3,4,5};

for (int& e:arr){     //& Lvalue reference

cout << e <<endl;

}

// using auto keyword

for(auto i : v)

std::cout <<i<<";

//using rvalue refence

for(auto&& i : V)

std::cout<<i<<";

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Null pointer

NULL is not keyword

#define included in standard libraries

int main(){

int*i=NULL;

}

leads to error error:use of undeclared identifier 'NULL'

in C++ 11 nullptr is a new keyword

it has its own type std::nullptr_t

it is implicitly convertible to any pointer

it is not impicitly convertible to integer or string

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Strongly typed enum

enum class Selection : int{

None, 

Single,

Multiple

};

Selectionsel = Seleection::Single; 

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Lambda expressions/functions

anonymouus function

Functions that are not going to be reuse

#include <iostream>

using namespace std;

int main(){

[]{};  //lambda definition

[]{}();  // lambda invocation

}

#include <iostream>

using namespace std;

int main(){

int count = 10;

[count]{cout<<"Count:"<<count<<endl;}();

}

output :

Count:10

//capture all @TODO

#include <iostream>

using namespace std;

int main(){

int count = 10;

int next = 11;

[=]{cout<<"Count:"<<count<<endl;

cout<<"Next:"<<next<<endl;}();

}

//capture by reference  @TODO

#include <iostream>

using namespace std;

int main(){

int count = 10;

[&count]{cout<<"Count:"<<count<<endl;

count =20;

}();

cout << 

}

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Automatic type detection during initialization

auto i =10; //i is an int

auto l =10LL; // L is an long long

auto p = new Instrument(); // p is a pointer to instrument

auto foo() -> int

{

return 42;

}

template <typename T>

auto foo (Tvalue)-->deltype(value.bar())

{

return value.bar()

}

C++ 14 makes the trainling return type unnecessary

auto foo()

{

return 42;

}

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Smart pointers 

Pointer capable of automatically deleting the heap memory allocated  when it goes out of scope

1)Unique Pointers

--> Light weight smart pointers

--> Unique _pptr object cannot be copied

--> Be cautious while using release

2) Shared Pointers

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Lvalue & Rvalue

lvalue has a name or memory address associate to it.

--> &x ( gives idnetifiable memory address)

 x      = 10

 |         |   

lvalue    Rvalue 

Lvalue reference

int var = 9

int &var_new = var; (Lvalue reference takes lvalue)

Rvalue is the right hand side of the assignment.

--> function return value is Rvalue

Rvalue reference

Std::move converts an lvalue to rvaluve

Move constructors

Move assignments 

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Pertfect forwarding

--> pass as it is

Std::forward<T>