20+ Clojure Interview Questions and Answers

Clojure is a modern, dynamic, and functional programming language known for its simplicity, expressiveness, and concurrency support. It typically runs on the Java Virtual Machine (JVM) and emphasises immutability and functional programming principles. 

Yes, it is possible to run Clojure on the JVM without using Java code. Clojure was initially designed as a hosted language on the JVM. This means it can fully leverage the JVM's capabilities with its own syntax and constructs without necessarily writing Java code. 

Here's how you can answer this question: "Immutable data structures are data structures that cannot be altered once created. In Clojure, immutability is a core concept because it leads to simpler, more predictable code and is suited for parallel programming by avoiding issues like data races and deadlock." 

You can answer this question like this: "In Clojure, a recursive function calls itself within its definition. To use recursion effectively and safely, Clojure often utilises tail call optimisation with the 'recur' keyword to avoid stack overflow errors." 

A macro in Clojure is a powerful feature that allows you to write code that manipulates and generates other code at compile time, offering a way to extend the language's syntax and capabilities. 

A lazy sequence in Clojure Loop is a sequence where the elements are computed on demand, whereas an eager sequence computes all its elements immediately. Lazy sequences are preferred when dealing with potentially large or infinite data sets to save memory and computational resources." 

Here's how you can answer this question: "Tail-recursive functions are an efficient way to implement recursion in Clojure. They help optimise recursive calls and prevent stack overflow errors, making them a preferred choice for certain types of recursive algorithms." 

You can answer this question like this: "To create a named function in Clojure, I would use the 'defn' keyword followed by the function name and parameters. The function body defines the operations to be performed." 

Here's how you can answer this question: "'defn' is used to define a regular function, while 'defmacro' is used to define a macro. While functions execute at runtime and take values as arguments, macros operate at compile-time and manipulate code directly." 

Meta-data in Clojure is used to associate extra information with various Clojure constructs like functions, variables, or data structures. This information can be used for documentation, type hinting, or other ancillary purposes. 

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STM, or Software Transactional Memory, is a concurrency control mechanism in Clojure. It allows for safe and automatic handling of concurrent processes, making it easier to write correct concurrent programs. 

You can answer this question like this: "'let' creates new, immutable bindings that are lexically scoped, while 'binding' creates mutable bindings that are dynamically scoped. 'let' is used for most local variable declarations, whereas 'binding' is used for changing the values of globally defined vars temporarily." 

Multimethods in Clojure provide a way to define a function that can behave differently based on its arguments' types or values, a concept known as polymorphism. Unlike traditional object-oriented polymorphism that's based on class hierarchy, multimethods use a more flexible dispatch mechanism based on runtime values or user-defined criteria. 

In Clojure, the '@' symbol is shorthand for the 'deref' function. It's used to dereference a reference type, like an atom, to get its current state or value. 

Transducers are a Clojure feature that provides a composable way to build algorithmic transformations independently of the context in which they are applied. They are likely to have a significant impact on how future versions of Clojure handle data transformation and processing. 

Different programming languages include a wide range of languages, each designed for specific purposes and paradigms. Examples include functional languages like Haskell, object-oriented languages like Java, scripting languages like Python, and many more. 

Clojure primarily runs on the Java Virtual Machine, leveraging its robust features. It can also target other platforms like JavaScript engines via ClojureScript. 

The JVM, or Java Virtual Machine, is an execution environment that allows Java-based applications (and those of JVM languages like Clojure) to run on any device or operating system that has the JVM installed. 

The main purposes of using Clojure Data Types on the JVM include benefiting from the JVM's performance and its vast ecosystem and libraries. Additionally, it allows for leveraging its cross-platform capabilities while employing a more functional and expressive programming paradigm. 

Clojure code is processed in several phases: reading, where code is parsed into data structures; macro expansion, where macros are evaluated and transformed; and compilation, where the code is compiled into JVM bytecode. 

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Clojure supports several versions of Java, typically aligning with the more recent and commonly used versions of the JVM for compatibility and performance reasons. 

You can answer this question like this: "To display the Clojure version in the REPL, you can use the command '(Clojure-version)', which will return the current version of Clojure that the REPL is using." 

In Clojure, functions can be either named or anonymous. They can be regular functions, higher-order functions that take other functions as arguments or return them, or special forms like macros.