Racket Interview Questions and Answers

1. What is Racket?

   • Answer: Racket is a family of programming languages, including a dialect of Lisp, designed for both research and practical programming. It emphasizes powerful macro systems, a rich set of libraries, and a focus on language-oriented programming.

2. What are the key features of Racket?

   • Answer: Key features include its homoiconicity (code is data), powerful macro system, multiple programming paradigms (functional, imperative, object-oriented), excellent tooling, and a large standard library.

3. Explain homoiconicity in Racket.

   • Answer: Homoiconicity means the language's code has the same structure as its data. This allows for powerful metaprogramming capabilities through macros, enabling the creation of domain-specific languages (DSLs) within Racket.

4. What is a macro in Racket?

   • Answer: A macro is a piece of code that transforms other code before it's evaluated. This allows for extending the language's syntax and creating new language constructs.

5. How do you define a function in Racket?

   • Answer: Functions are defined using `(define (function-name arg1 arg2 ...) body)`. For example: `(define (add x y) (+ x y))`

6. Explain the difference between `define` and `let` in Racket.

   • Answer: `define` creates a variable binding that is visible throughout the current scope (or globally if at the top level). `let` creates local bindings within a specific block of code.

7. What are the different data types in Racket?

   • Answer: Racket has various data types including numbers (integers, floating-point), booleans (#t, #f), symbols, strings, lists, vectors, pairs, and more.

8. How do you create a list in Racket?

   • Answer: Lists are created using parentheses. For example: `'(1 2 3 4)` creates a list containing the numbers 1 through 4.

9. How do you access elements of a list in Racket?

   • Answer: You can access elements using `car` (first element) and `cdr` (rest of the list). For example: `(car '(1 2 3))` returns 1, and `(cdr '(1 2 3))` returns `'(2 3)`.

10. What is pattern matching in Racket?

    • Answer: Pattern matching allows you to elegantly extract data from structured data types like lists or records. It's often used with `match` expressions.

11. Explain the concept of continuations in Racket.

    • Answer: Continuations represent the rest of the computation that needs to be performed after a particular point. They are a powerful concept that enables advanced control flow mechanisms.

12. What are modules in Racket? How are they used?

    • Answer: Modules are used to organize code into reusable units. They are defined using `(module module-name (require ...) ...)` and allow for controlled import/export of variables and functions.

13. How do you handle exceptions in Racket?

    • Answer: Exceptions are handled using `with-handlers`. You specify handlers for specific exception types, and the corresponding handler code executes if an exception of that type is raised.

14. What is the purpose of the `require` form in Racket?

    • Answer: `require` imports modules or libraries into the current scope, making their functions and definitions available.

15. Explain the difference between `let` and `letrec` in Racket.

    • Answer: `let` creates bindings where the values are computed before the bindings are created. `letrec` allows for mutually recursive bindings, where the values can depend on each other.

16. What are some common libraries used in Racket?

    • Answer: Common libraries include `racket/base`, `racket/gui`, `racket/match`, `racket/class` (for object-oriented programming), and many others depending on the application.

17. How would you write a recursive function to calculate the factorial of a number in Racket?

    • Answer: `(define (factorial n) (if (= n 0) 1 (* n (factorial (- n 1)))))`

18. How would you implement a simple linked list in Racket?

    • Answer: A simple linked list can be represented using pairs. A node would be a pair: `(cons value next-node)`. The empty list is `'()`. Functions like `cons`, `car`, and `cdr` would be used to manipulate the list.

19. What is the purpose of the `#lang` declaration in a Racket file?

    • Answer: The `#lang` declaration specifies the language dialect or reader to use for the file. It determines the language's syntax and semantics.

20. How do you perform input/output operations in Racket?

    • Answer: Input/output is typically done using functions like `read`, `read-line`, `display`, `write`, and others provided by the standard library.

21. Explain how to create a simple GUI application in Racket.

    • Answer: The `racket/gui` library provides tools for creating GUI applications. It involves creating frames, buttons, text fields, and other widgets and handling events.

22. How does Racket's garbage collection work?

    • Answer: Racket uses a garbage collector to automatically manage memory. It reclaims memory that is no longer being used, preventing memory leaks.

23. What are some advantages of using Racket for functional programming?

    • Answer: Advantages include its built-in support for immutability, first-class functions, higher-order functions, and powerful tools for working with functional data structures.

24. How can you create a macro that expands to a function call?

    • Answer: You can use `syntax-rules` or more advanced macro systems to define a macro that transforms code into a function call. The syntax would depend on the desired transformation.

25. What are some of the limitations of Racket?

    • Answer: Limitations can include a smaller community compared to some mainstream languages, and a steeper learning curve due to its powerful but sometimes complex features.

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