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Racket is a general-purpose, multi-paradigm programming language that belongs to the Lisp-Scheme family. It is designed with an emphasis on functional programming and includes significant support for object-oriented, imperative and logic-based paradigms as well. Racket's core philosophy revolves around extensibility and modularity; it encourages programmers to create new domain-specific languages or extend existing ones. One of its unique features is the ability to build graphical user interfaces (GUIs), web servers, scripts etc., directly in Racket without needing external libraries. It also provides extensive support for metaprogramming through macros. Racket comes bundled with DrRacket which is a fully-featured integrated development environment (IDE) making it suitable for both professional software development and teaching purposes due its pedagogic design. The language supports various data types including numbers, strings, lists etc., along with more complex structures like vectors or hash tables. Its standard library offers numerous built-in functions covering areas such as file I/O operations, network communication or mathematical computations among others. Overall Racket can be used in diverse fields ranging from scripting over web-development up to research in programming-language design itself due its highly flexible nature combined with powerful abstractions mechanisms provided by the language system itself.

Ask the right questions secure the right Racket talent among an increasingly shrinking pool of talent.

First 20 minutes

General Racket app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Racket application development, including their experience with various programming languages, databases, and their approach to designing scalable and maintainable systems.

How would you define a function in Racket?

You can define a function in Racket using the 'define' keyword. For example, '(define (add a b) (+ a b))' defines a function named 'add' that takes two parameters and returns their sum.

What are the basic data types in Racket?

The basic data types in Racket include numbers, strings, booleans, lists, vectors, hash tables, and more. Racket also supports user-defined data types.

How would you create a list in Racket?

You can create a list in Racket using the 'list' function. For example, '(list 1 2 3)' creates a list of three elements.

Describe the difference between 'let' and 'let*' in Racket.

'let' and 'let*' are both used to bind variables in Racket. The difference is that 'let' bindings are simultaneous, while 'let*' bindings are sequential. This means that in a 'let*' expression, later bindings can refer to earlier ones.

How would you implement recursion in Racket?

Recursion in Racket is implemented by having a function call itself. For example, a recursive function to calculate the factorial of a number could be defined as follows: '(define (factorial n) (if (zero? n) 1 (* n (factorial (sub1 n)))))'.

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What you’re looking for early on

Has the candidate demonstrated a strong understanding of Racket's syntax and semantics?

Does the candidate have a good grasp of functional programming concepts?

How well can the candidate debug and optimize Racket code?

How familiar is the candidate with using Racket's built-in libraries and tools?

Next 20 minutes

Specific Racket development questions

The next 20 minutes of the interview should focus on the candidate's expertise with specific backend frameworks, their understanding of RESTful APIs, and their experience in handling data storage and retrieval efficiently.

What are macros in Racket and how would you define one?

Macros in Racket are used to define new syntactic constructs. You can define a macro using the 'define-syntax' keyword, followed by the name of the macro and a transformer that specifies how the macro should be expanded.

Describe the difference between 'eq?', 'eqv?', and 'equal?' in Racket.

'eq?', 'eqv?', and 'equal?' are all used to compare values in Racket. 'eq?' tests whether its arguments are the same object, 'eqv?' tests whether its arguments are the same value in some sense, and 'equal?' tests whether its arguments are structurally equivalent.

How would you handle exceptions in Racket?

Exceptions in Racket can be handled using the 'with-handlers' function, which takes a list of handlers and an expression to evaluate. Each handler is a function that takes an exception as argument and returns a value.

What are contracts in Racket and how would you use them?

Contracts in Racket are a way to specify the expected behavior of a function. You can use the 'contract' function to attach a contract to a function. For example, '(contract (-> number? number?) add)' specifies that the 'add' function should take two numbers as input and return a number.

Describe the difference between 'map', 'for/list', and 'for-each' in Racket.

'map', 'for/list', and 'for-each' are all used to apply a function to each element of a list in Racket. The difference is that 'map' and 'for/list' return a new list of results, while 'for-each' returns void and is used for its side effects.

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At this point, a skilled Racket engineer should demonstrate strong problem-solving abilities, proficiency in Racket programming language, and knowledge of software development methodologies. Red flags include lack of hands-on experience, inability to articulate complex concepts, or unfamiliarity with standard coding practices.

Digging deeper

Code questions

These will help you see the candidate's real-world development capabilities with Racket.

What does this simple Racket code do?
(define (square x) (* x x))
This code defines a function named 'square' that takes one argument 'x' and returns the square of 'x'.
What will be the output of this Racket code?
(define x 5) (define y 10) (if (> x y) 'yes 'no)
The output of this code will be 'no'. It first defines two variables 'x' and 'y' with values 5 and 10 respectively. Then it checks if 'x' is greater than 'y'. If 'x' is greater, it will return 'yes', otherwise 'no'. Since 5 is not greater than 10, it returns 'no'.
What does this Racket code do that involves list manipulation?
(define (sum-list lst) (if (null? lst) 0 (+ (car lst) (sum-list (cdr lst)))))
This code defines a function named 'sum-list' that takes a list 'lst' as an argument and returns the sum of all elements in the list. It uses recursion to traverse the list and add up the elements. If the list is empty, it returns 0.
What does this Racket code do that involves concurrency?
(define (parallel-sum lst) (let-values ([(a b) (split-at lst (quotient (length lst) 2))]) (+ (thread-wait (thread (lambda () (sum-list a)))) (thread-wait (thread (lambda () (sum-list b)))))))
This code defines a function named 'parallel-sum' that takes a list 'lst' as an argument and returns the sum of all elements in the list. It splits the list into two halves, then creates two separate threads to calculate the sum of each half concurrently. The 'thread-wait' function is used to wait for each thread to finish and return its result. The results are then added together to get the final sum.

Wrap-up questions

Final candidate for Racket Developer role questions

The final few questions should evaluate the candidate's teamwork, communication, and problem-solving skills. Additionally, assess their knowledge of microservices architecture, serverless computing, and how they handle Racket application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

How would you implement a higher-order function in Racket?

A higher-order function in Racket is a function that takes other functions as arguments or returns a function as result. For example, '(define (compose f g) (lambda (x) (f (g x))))' defines a higher-order function 'compose' that takes two functions 'f' and 'g' and returns a new function that applies 'g' to its argument and then applies 'f' to the result.

What are continuations in Racket and how would you use them?

Continuations in Racket represent the future of a computation. You can capture the current continuation with the 'call/cc' function, and later invoke it to resume the computation from that point. This can be used to implement advanced control structures such as coroutines or backtracking.

Describe the difference between 'set!' and 'set-mcdr!' in Racket.

'set!' and 'set-mcdr!' are both used to mutate data in Racket. The difference is that 'set!' changes the value of a variable, while 'set-mcdr!' changes the cdr (tail) of a pair. This means that 'set-mcdr!' can be used to modify lists in place.

Racket application related

Product Perfect's Racket development capabilities

Beyond hiring for your Racket engineering team, you may be in the market for additional help. Product Perfect provides seasoned expertise in Racket projects, and can engage in multiple capacities.

Racket Consultive assessments

Racket Application Conversion Assessment Racket Application Integration Assessment Racket Data & Database Integration Assessment

Custom Racket development projects

Custom Racket App Conversion Racket Custom App Development Process App UI Design for Racket Facelifts

Hiring guide for Racket Engineers

Racket Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

What you’re looking to see on the Racket engineer at this point.

Racket Consultive assessments

Custom Racket development projects