Functional Programming versus Object Oriented Programming

Functional programming is the programming technique that accentuates the functional factors required for creating and implementing the programs. OOP or the Object-Oriented Programs are the conceptual programming techniques that uses objects as the key. The programming model used in functional programming is a declarative programming model, while object-oriented programming uses the imperative programming model. In functional programs, variables and functions are the main elements of the code, while in object-oriented programs, objects and methods are the key elements.

Functional Programming

Functional programming also supports the programming languages like Lisp, Clojure, Wolfram, Erlang, Haskell, F#, R, and other prominent and domain-specific languages. Functional programming is a great fit for data science work, and R is the popular language among data scientists.

FP languages can be translated well into an interactive environment, which makes the understanding of code easier.

Functional programming provides advantages like efficiency, lazy evaluation, nested functions, bug-free code, parallel programming. In simple language, functional programming is to write the function having statements to execute a particular task for the application.

The function can be easily invoked and reused at any point.  It also helps the code to be managed, and the same thing or statements does not need to write again and again.

Functional Programming based on different concepts is 1. High Order Functions (HOF). 2. Pure functions. 3. Recursion. 4. Strict and Non-strict Evaluation. 5. Type systems. 6. Referential Transparency. In functional programming, functions are referred to as first-class citizens.

OOP (Object-Oriented Programming)

Object-oriented programming based on the main features that are:

1. Abstraction: It helps in letting the useful information or relevant data to a user, increasing the program’s efficiency and making things simple. 
2. Inheritance: It helps in inheriting the methods, functions, properties, and fields of a base class in the derived class.
3. Polymorphism: It helps in doing one task in many ways with the help of overloading and overriding, which is also known as compile-time and run-time polymorphism, respectively. 
4. Encapsulation: It helps in hiding irrelevant data from a user and prevents the user from unauthorized access.

Object-oriented programming languages are C++, C#, Java, Python, Ruby, PHP, Perl, Objective-C, Swift, Dart, Lisp, etc. In an object-oriented application, objects can be easily reused in another application. New objects can be easily created for the same class, and code can be easily maintained and altered.

It also has the feature of memory management. It provides a great benefit in designing large programs, which can be easily divided into smaller parts and helps in distinguishing the components or phases that need to be executed or planned in a certain way.

The main deal with OOP is the ability to encapsulate data from outsiders. Encapsulation is the ability to hide variables within the class from outside access — which makes it great for security reasons, along with leaky, unwanted or accidental usage. Most programmers using object oriented design say that it is a style of programming that allows you to model real world scenarios much simpler. This allows for a good transition from requirements to code that works like the customer or user wants it to.

Functional Programming and OOP Comparison Table

Following is the Comparison Table Between Functional Programming and OOP

BASIS FOR COMPARISON	Functional Programming	OOP
Definition	Functional programming emphasizes an evaluation of functions.	Object-oriented programming based on a concept of objects.
Data	Functional programming uses immutable data.	Object-oriented uses mutable data.
Model	Functional programming does follow a declarative programming model.	Object-oriented programming does follow an imperative programming model.
Support	Parallel programming supported by Functional Programming.	Object-oriented programming does not support parallel programming.
Execution	In Functional programming, the statements can be executed in any order.	In OOPs, the statements should be executed in a particular order.
Iteration	In Functional programming, recursion is used for iterative data.	In OOPs, loops are used for iterative data.
Element	The basic elements of functional programming are Variables and Functions.	The basic elements of object-oriented programming are objects and methods.
Use	Functional programming is used only when there are few things with more operations.	Object-oriented programming is used when there are many things with few operations.

OOP encourages organizing code in terms of interfaces by encapsulating complex data in objects so the complexity can’t be accessed directly. This tends to help with maintainability because you can change the implementation in one place without fear of breaking your code for the outside world. Because many FP languages do not enforce this separation of implementation and interface, it takes more discipline to organize codebases in a modular way.

Pros of Object Oriented languages vs. Functional Programing languages:

• Languages where “everything is an object” are extremely useful; i.e. languages where things like types and classes and even the code of the program itself are objects. This allows a phenomenal amount of flexibility—but unfortunately it isn’t the case in many of the more popular OO languages, like Java, C++, C# and many others. Python and Ruby have this behavior (along with Smalltalk, of course).

• From a purely syntactic standpoint, it’s quite convenient that any object will offer code completion for all of its methods in an IDE. This is especially helpful when learning new languages and libraries.

Cons of OOP languages vs. FP languages:

• Functional programming languages make it more natural to write code without side effects, which in turn makes program behavior easier to reason about, especially in a highly concurrent context.

• Statically typed functional languages tend to be much more polymorphic than statically typed OO languages both because they have much more expressive ways to annotate types than OO languages and because polymorphism doesn’t depend on a hierarchical relationship between types. (i.e. inheritance)

• For the above reason, and because of first-class functions, code in functional languages tends to be more composable between different libraries.

• Type systems in statically typed functional languages also tend to prevent more errors by making null pointer errors impossible and forcing programmers to account for all type variation in unions.

Applications of Functional programming

• Functional programming languages are frequently favoured over commercial software development for academic objectives.                            
• Nonetheless, numerous popular functional programming languages, such as Clojure, Erlang, F#, Haskell, and Racket, are widely utilised for developing a wide range of commercial and industrial applications.
• WhatsApp makes use of Erlang, to enable its 100+ staff to manage the data of over 1.5 billion people, the company developed a programming language based on the functional programming paradigm.
• Another important torchbearer of the functional programming style is Haskell. It is used by Facebook in its anti-spam system. Even JavaScript, one of the most widely used programming languages, flaunts properties of a dynamically typed functional language.
• Furthermore, for diverse programming languages to dominate in different fields, the functional style of programming is required. For instance, in statistics, R, and in financial analysis, J, K, and Q.
• Domain-specific declarative languages like Lex/Yacc and SQL leverage some parts of this programming paradigm to avoid using changeable values.