C++ Archives - SimpleTechTalks

C++11: Override and Final keyword

The explicit override and final keywords in C++11 (Introduction to C++11) enhances the polymorphism capabilities of C++. These new features provide extra control over virtual functions to the programmer. In this post, we will discuss about these new features and their usage.

Override

The explicit override keyword overrides the marked virtual function in derived class as override version of base class virtual functions. This ensures that the overrides are done by the programmer intentionally which reduces the chances of unwanted mistakes by providing clarity and hence improves the code readability and maintainability.

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C++11: Uniform Initialization explained with Simple example

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In C++11 (Introduction to C++11), “Uniform initialization” syntax is introduced to initialize variables which provides a consistent syntax for all types of data variables initialization. This syntax is defined for all types of objects, arrays etc. In this post we are focusing on Uniform initialization syntax with some coding examples.

Earlier there were multiple ways to initialize variables. For example: basic data type variables could be initialized using assignment operator whereas class objects could be initialized using a constructor.

In C++11, a uniform way of initializing variables is introduced which is called “Uniform Initialization” syntax.

Let’s have a look at the sample code example to understand the usage of uniform initialization.

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C++11: Initializer Lists Explained with Simple Example

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In C++11 (Introduction to C++11), Initializer lists are a major addition to the C++ language. In this post we are focusing on Initializer lists with some coding examples.

To understand Initializer lists, we need to first understand the constructors. Constructors are special member functions of a class which is used to initialize the object in desired way. Constructors has the same name as that of class. There could be multiple constructors defined in a class which could be selected based on invoking conditions.

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std::bitset explained with simple example

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A Bitset is a standard template library class provided by C++ which can be used to define a fixed length sequence of bits. A value of zero indicates bit is unset whereas 1 indicates bit is set.
This class provides similar functionality as array of Boolean values in more space efficient way. There are lot of useful memory functions also provided by the library which can be used by the programmers to use it directly.

Let’s have a look into std::bitset template class definition.

template <size_t N> class bitset;
Where N = length of bitset (in bits).

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std::vector explained with simple example

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Vector in C++ are part of Standard Library Container Classes which basically has the functionality of dynamic array which are flexible in size.
C++ STL provides a template class definition for Vectors which are very efficient, refined, and easy to use.
It also has lots of very useful member functions which can be used directly in programs for faster implementation.

Let’s have a look into std::vector class template definition.

template <class T, class Allocator = allocator<T>> class vector
where T = data type that is being stored and allocator defines the allocator functions.

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Difference between Copy constructors and Assignment operator

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Copy constructor is a special kind of constructor which initializes an object using another object. Compiler always provides a default copy constructor but if needed it can be over-ridden by programmer to meet the requirements.

Assignment operator is basically assigning the new values to already created object. In this case object initialization doesn’t happen as it is already done.

For eg:

class Base{
};

Base b1;
Base b2 = b1; /* Copy constructor as initialization also needs to done */
Base b3;
b3 = b2; /* Assignment operator as object is already created */

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Difference between Constructors and Destructors

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Constructor

Constructors are special member functions of a class which is used to initialize the object in desired way. Constructors has the same name as that of class. There could be multiple constructors defined in a class which could be selected based on invoking conditions.

Types of constructor

Default constructor – Any constructor without argument is called default constructor.
Parameterized constructor – Any constructor in which argument can be passed is called Parameterized constructor.
Copy constructor – This is a special kind of constructor which uses an existing object to create a new object.

Destructor

Destructor is a special member function of a class which is used to delete the object. Destructor also has the same name as that of class prefixed with “~” sign. In any class, one could define only one destructor. Destructor doesn’t take any argument.

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Smart Pointers Explained With Simple Example

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Standard library included with C++ compilers provides some specific resource management pointers classes which are also called as Smart Pointers.

A normal (raw) pointer typically points to an object, but it doesn’t indicate who owns the objects. This leads to the confusion most of the times, that who is supposed to delete the pointer and free the memory.
Also, by looking into the pointer, one can’t guess how the pointer should be deleted.

Smart pointers are designed to overcome these shortcomings of raw pointers.

Types of Smart Pointers

unique_ptr -> This pointer class has the exclusive ownership.
shared_ptr -> This pointer class has the shared ownership.
weak_ptr -> This pointer class is used with shared_ptr and it doesn’t have any ownership. This pointer is typically used to break loops into circular data structures.

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C++11: extern template Explained With Simple Example

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In C++11 (Introduction to C++11), extern template is added to optimize the compile time and object size. Earlier C++ compiler (C++ 03) instantiate a template function or class whenever it encounters a fully defined template function or class. If the template is used in multiple files, then compiler must create multiple instances of template function or class only to later discard all the instance but one. This would result in extra compile time and increased object file size. In C++ 03 there was no way to avoid this.

In C++11, extern template feature is introduced to avoid this situation.
Format of extern template is as follows

extern template void DemoTemplateFunction <int> ();
extern template class NUM <type>;

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Early vs Late Binding using Virtual Table and VPtr

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Early Binding	Late Binding
Happens at compile time.	Happens at run time.
Compiler has all information to invoke correct function version at compile time.	Compiler doesn’t have information to identify correct function version.
Normal function calls are example of Early Binding.	Virtual functions are example of Late Binding.
Functions invoked by object is example of early binding	Functions invoked by pointers can be example of late binding.
Early binding is efficient as no cost paid at run-time for function resolution.	Late Binding is slightly costly as function resolution happens at run time.
Early binding doesn’t provide flexibility of one method multiple interfaces.	Late Binding provide flexibility.
Doesn’t have any virtual table or virtual pointer.	It uses Virtual Table and Virtual Pointer.

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