Author
Swaminathan Iyer
Product @ Interview Kickstart | Ex Media.net | Business Management - XLRI Jamshedpur. Loves building things and burning pizzas!
Have you heard of Functional Programming? Want to know what all the buzz is about? If you’re looking to learn more about FP, the best languages for functional programming, and FP interview questions, you’ve come to the right place — this article covers all this and more!
If you are preparing for a tech interview, check out our technical interview checklist, interview questions page, and salary negotiation e-book to get interview-ready! Also, read Python String join() Method, Sum Function in Python, and How to Read and Write Files in Python for more specific insights and guidance on Python concepts and coding interview preparation.
Having trained over 9,000 software engineers, we know what it takes to crack the most challenging tech interviews. Since 2014, Interview Kickstart alums have been landing lucrative offers from FAANG and Tier-1 tech companies, with an average salary hike of 49%. The highest ever offer received by an IK alum is a whopping $933,000!
At IK, you get the unique opportunity to learn from expert instructors who are hiring managers and tech leads at Google, Facebook, Apple, and other top Silicon Valley tech companies.
Want to nail your next tech interview? Sign up for our FREE Webinar.
In this article, we’ll cover:
Functional programming represents a programming paradigm that aims to bind all things in pure mathematical functions based on lambda calculus. In other words, FP is an approach to software construction based on creating pure functions. FP helps in solving problems where many different operations need to be performed on the same data set. Some common use cases of FP include AI applications like machine learning, speech and vision modeling, and language processing.
Here are some more interesting facts about FP:
There are some languages specially designed for functional programming, and some that aren’t but do support it. We’ll now learn more about these languages and learn what this means.
Functional programming languages are languages specially designed for functional programming and aim to mimic mathematical functions. FP languages are designed for handling list processing applications, symbolic computation, and support all characteristics associated with functional programming.
FP languages can be of two types:
The following table lists some of the most notable and popular programming languages that support functional programming. Note that while all these languages support functional programming significantly, some are not considered FP languages.
Language
Considered FP Language or not?
Haskell
FP
Clojure
FP
Scala
Not FP
Erlang
FP
Common Lisp
FP
Clean
FP
SML
FP
Python
Not FP
ML/Scheme/OCamI Lisp
FP
F#
FP
SQL
Not FP
XSLT
Not FP
Mathematica
FP
In essence, here are some prominent characteristics of functional programming:
While FP languages are used more for academic than commercial software development purposes, many FP languages like Haskell, Clojure, Erlang, etc., are extensively used for industrial and commercial application development. Here are some examples:
Functional Programming
Object-Oriented Programming
FP uses immutable data
OOP uses mutable data
FP follows the Declarative Programming Model
OOP follows the Imperative Programming Model
FP focuses on “what to solveâ€
OOP focuses on “how to solveâ€
FP supports Parallel Programming
OOP isn’t best for Parallel Programming
FP functions have no-side effects
OOP functions can cause significant side effects
Flow control is done using recursion and function calls instead of loops and conditionals
Flow control is done using loops and conditional
FP uses recursion to iterate
OOP uses loops to iterate
Order of execution of statements isn’t
that important
Order of execution of statements is critical
Supports abstraction over
data as well as behavior
Supports abstraction only over data
An efficient program causes minimum overhead and risk due to decreased space and time resource requirements and is also not a serious risk for the operating environment.
A program’s efficiency depends on several factors and can be increased by optimizing for these factors. Here are some tips and factors to look out for that can increase the efficiency of your code. The trick is to optimize for algorithmic efficiency and execution speed in all ways possible:
If you’re great at functional programming in a language relevant to a company, it can significantly increase your chances of getting hired. As mentioned above, Facebook uses Haskell and WhatsApp uses Erlang.
Many other companies like AT&T, Bank of America, Galois, Intel, and NVIDIA use Haskell. Foursquare uses Scala. Honing your FP skills, especially in a language relevant to your target company, is a worthwhile investment and will help you nail your big-tech interview.
Here are some FP based interview questions to help you evaluate your understanding of the topic:
1. What is “modular design,†and why is it important?
Modular design involves using small modules independent from each other, which can be coded quickly, re-used often, and tested separately. This increases productivity and makes development more efficient.
2. What are first-class and higher-order functions?
First-class functions have no regular restrictions on use, can be treated just like variables, and can be found anywhere in the code.
Higher-order functions either take other functions as arguments or return other functions as results, or both.
3. What are pure and impure functions?
In pure functions, Inputs are declared as inputs and aren’t ever hidden. Outputs are also declared as outputs, and each time the output is the same if given the same parameters. They act on their parameters and are inefficient if they’re not returning anything. In impure functions, at least some inputs and outputs are hidden, and since they have dependencies, they cannot be used or tested separately.
Pure Function
Impure Function
function pureExample(num1,num2)
{
return num1*num2;
}
int num1;
function impureExample(){
num1 = num1*5;
}
4. What is the concept of side effects in functional programming?
State changes that occur anywhere other than inside of a called function are called side effects, which FP aims to minimize as much as possible by separating them from the remaining software.
5. How does a capable compiler run code written in functional programming style?
A capable compiler would run by parallelizing the instructions written in FP style code, would wait for the results to be evaluated, and can memorize the result as needed.
Whether you’re a Coding Engineer gunning for Software Developer or Software Engineer roles, a Tech Lead, or you’re targeting management positions at top companies, IK offers courses specifically designed for your needs to help you with your technical interview preparation.
If you’re looking for guidance and help with getting started, sign up for our FREE webinar. As pioneers in the field of technical interview preparation, we have trained thousands of software engineers to crack the most challenging coding interviews and land jobs at their dream companies, such as Google, Facebook, Apple, Netflix, Amazon, and more!
Time Zone:
Get your enrollment process started by registering for a Pre-enrollment Webinar with one of our Founders.
The 11 Neural “Power Patterns” For Solving Any FAANG Interview Problem 12.5X Faster Than 99.8% OF Applicants
The 2 “Magic Questions” That Reveal Whether You’re Good Enough To Receive A Lucrative Big Tech Offer
The “Instant Income Multiplier” That 2-3X’s Your Current Tech Salary
The 11 Neural “Power Patterns” For Solving Any FAANG Interview Problem 12.5X Faster Than 99.8% OF Applicants
The 2 “Magic Questions” That Reveal Whether You’re Good Enough To Receive A Lucrative Big Tech Offer
The “Instant Income Multiplier” That 2-3X’s Your Current Tech Salary
Just drop your name and email so we can send your Power Patterns PDF straight to your inbox. No Spam!
By sharing your contact details, you agree to our privacy policy.
Time Zone: Asia/Dhaka
We’ve sent the Power Patterns PDF to your inbox — it should arrive in the next 30 seconds.
📩 Can’t find it? Check your promotions or spam folder — and mark us as safe so you don’t miss future insights.
We’re hosting a private session where FAANG insiders walk through how they actually use these Power Patterns to crack interviews — and what sets top performers apart.
🎯 If you liked the PDF, you’ll love what we’re sharing next.
Time Zone:
