CodeSubmit Interview Series

The 10 Best Clojure Interview Questions in 2023

What are the best Clojure interview questions? If you’re wondering what questions to ask your Clojure candidates, this is the list for you. Read on!

Interviewing Clojure developers 

Clojure is a functional and dynamic dialect of Lisp on the Java platform. Clojure uses Lisp as a macro system and treats code as data, advocating immutability and immutable data structures. It encourages developers to be explicit about managing identity and its states. 

This is intended to enable the development of robust, fast, and simple programs. Clojure’s type system is dynamic, but a dependent type system can be possible in the future.  

Now, want to learn what the best Clojure interview questions are? Let’s go!

Beginner Clojure interview questions

What are the top junior Clojure developer questions? That’s what we’ll explore in this section.

1. What are the benefits of Clojure? 


One of the main benefits of Clojure is that it works well on multiple platforms, including JavaScript, Node.js, and Java Virtual Machine. Clojure is also beneficial because it:

  • Is intense and well-designed, thanks to Lisp. 

  • Provides many functionalities that make it easy to operate on sequences, where Java collections, strings, streams, XML trees, and more are treated. 

  • It supports many types of languages, including JavaScript, Java, Ruby, and C++, as well as data types, such as Boolean, decimals, characters, and strings. 

  • Supports the dynamic implementation of Java interfaces and classes.

  • Can run on multiple platforms without needing changes.

  • Provides an interactive development environment.

2. What are the cons of Clojure? 


Clojure doesn’t have an efficient memory, which increases the cost of the hardware. It can’t be used for real-time or soft real-time services, which prevents it from being useful in some cases. Plus, Clojure can’t be used for the performance of low-level languages or code, including C++, Rust, and C. Clojure also takes a bit more time to master because it is a more extensive language. 

3. What functions are used in Clojure? 


The types of functions that are used in Clojure are anonymous functions, which are simple functions that aren’t bound to a name, named functions, which are bound to a symbol used as an identifier, and high order functions, which usually take other functions as a parameter. 

4. What are some variables in Clojure? 


Clojure variables include int, long, short, char, boolean, string, and float. 

Int is used to represent whole numbers, short represents a short number, long represents a long number, and float represents 32-bit floating point numbers. Char, on the other hand, defines a single character literal, boolean represents a boolean value (it can be true or false), and string are text literals, which are represented as a chain of characters. 

Advanced Clojure interview questions

Let’s move on to the best Clojure interview questions for senior developers. Here you go: 

5. What is Clojure REPL and why is it used? 


REPL (Reading Eval Print Loop) is a programming environment, which makes it possible to interact with a running Clojure program. Clojure REPL also enables the program to be modified by evaluating one code expression at a time. 

Thanks to Clojure REPL, the development experience becomes interactive. The developer can first perform small tasks manually and then make them increasingly automated until the function is programmed. And during debugging, developers can quickly reproduce the problem, observe the symptoms, and then improvise experiments to narrow down the cause of the bug. 

In fact, REPL is one of the main reasons developers use Clojure. REPL can be used in varying situations, such as to launch local development environments, run automated test suites, debug, orchestrate remote machines, and get familiar with libraries and APIs. 

6. Explain the difference between a lazy and an eager sequence. 


A lazy sequence isn’t evaluated until it’s needed. An eager sequence, on the other hand, is evaluated as soon as it’s created. Lazy sequences are in some ways more efficient as they aren’t evaluated right away, but at the same time, they’re harder to debug. 

7. Define Map in Clojure. 


Map is a collection that holds key-value pairs and the values stored in the map can be accessed with the corresponding key. There are two types of maps, HashMaps and SortedMaps. 

HashMaps are created with the hash-map function and their keys support hashCode and equals. 

SortedMaps are created with the sorted-map function and their keys implement an instance of Comparable. The elements of SortedMap are sorted according to their keys. 

8. Explain agents in Conjure. 


Agents are a concurrent data structure that is used to manage state by asynchronously sending and receiving messages to update its state. Agents would be used when a concurrent data structure is needed to be updated asynchronously. 

9. Explain special variables. 


There are two special variables in Clojure. These are &form, which is the actual form that is being invoked, and &env, a map of local bindings from symbols to objects holding compiler information about that binding. Special variables are available inside defmacro for advanced use. 

10. Explain atoms.


Atoms are a basic data type in Clojure, which are immutable and important for concurrent processing. Atoms can be shared between threads without the data being corrupted.

Over to you!

There you have it! Now you know what the top Clojure interview questions are. 

The next step is to conduct your interviews. But your hiring process doesn’t end there.

You also need to test developers. And that’s best done with developer assessment tests. 

At CodeSubmit, we offer take-home challenges and CodePair live challenges.

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