Hiring guide for Object Lisp Engineers

Object Lisp Developer Hiring Guide

Lisp, an acronym for List Processing, is a programming language that stands as a paragon of elegance in the world of computer science. Its inception can be traced back to 1958 when it was conceived by John McCarthy at Massachusetts Institute of Technology (MIT). The language embodies one of the earliest and most profound contributions to the realm of artificial intelligence, cementing its status as an immortal legend in computational history. The allure and mystique surrounding Lisp are primarily derived from its unique linguistic structure. It is characterized by its fully parenthesized prefix notation which may seem unconventional or even daunting at first glance but provides unmatched clarity and precision once understood. This highly distinctive feature allows programs written in Lisp to manipulate their own code as data - a concept known as homoiconicity - thus making it one among few languages that possess this remarkably powerful characteristic. Lisp's design philosophy epitom

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

First 20 minutes

General Object Lisp app knowledge and experience

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

What are the basic data types in Lisp?
The basic data types in Lisp are: integers, symbols, cons cells, strings, arrays, structures, and functions.
How would you define a function in Lisp?
In Lisp, functions are defined using the DEFUN keyword. For example, to define a function that adds two numbers, you would write: (defun add (x y) (+ x y))
What is the purpose of the 'cons' function in Lisp?
'cons' is a fundamental function in Lisp used to construct new lists or pairs. It takes two arguments and returns a newly allocated pair with the first argument as the CAR and the second argument as the CDR.
Describe the difference between 'eq', 'eql', 'equal', and 'equalp' in Lisp.
'eq' tests if two items are the exact same object, 'eql' is like 'eq' but also compares numbers of the same value and character literals, 'equal' tests for structural equality, and 'equalp' is like 'equal' but also considers strings of different cases and numbers of different types to be equal.
What are macros in Lisp and why are they useful?
Macros in Lisp are a way to define new syntax or new control structures. They are useful because they allow programmers to extend the language in ways that suit their specific needs.
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What you’re looking for early on

Does the candidate demonstrate a deep understanding of Object Lisp?
Is the candidate able to articulate complex concepts clearly?
Can the candidate provide examples of past projects where they used Object Lisp?
Does the candidate show good problem-solving skills?

Next 20 minutes

Specific Object Lisp 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.

How would you implement a loop in Lisp?
A loop can be implemented in Lisp using recursion or built-in looping constructs like 'do', 'dotimes', and 'dolist'. Recursion is a fundamental concept in Lisp, but for simple iterations, built-in looping constructs are usually more convenient.
What is tail recursion in Lisp and why is it important?
Tail recursion in Lisp is a form of recursion where the recursive call is the last operation in the function. It's important because it allows the Lisp interpreter to optimize the recursion, resulting in more efficient code.
What are the different types of variables in Lisp?
There are two main types of variables in Lisp: local and global. Local variables are defined within a function and are not accessible outside of it. Global variables, also known as special variables, are accessible throughout the entire program.
How would you handle errors in Lisp?
Errors in Lisp can be handled using the 'condition-case' construct, which allows you to specify handlers for different types of errors. You can also use the 'error' function to signal an error.
Describe the difference between a symbol and a variable in Lisp.
In Lisp, a symbol is an object that has a name, and it can be used to represent various things such as variables, functions, or constants. A variable, on the other hand, is a symbol that has been given a value.
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The ideal back-end app developer

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

At this point, a skilled Object Lisp engineer should demonstrate strong problem-solving abilities, proficiency in Object Lisp 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 Object Lisp.

What does this simple Lisp code do?
(defun square (n) (* n n))
This code defines a function named 'square' that takes one argument 'n'. It returns the square of 'n' by multiplying 'n' by itself.
What will be the output of this Lisp code?
(let ((x 5) (y 10)) (+ x y))
This code will output 15. It first defines two local variables 'x' and 'y' with values 5 and 10 respectively, then it adds these two variables together.
What does this Lisp code do with the list?
(mapcar #'(lambda (x) (* x x)) '(1 2 3 4 5))
This code squares each element in the list '(1 2 3 4 5)'. 'mapcar' applies the function to each element of the list and returns a new list with the results.
What does this Lisp code do related to threading?
(bt:make-thread #'(lambda () (print 'Hello, World!)))
This code creates a new thread that prints 'Hello, World!' to the standard output. 'bt:make-thread' is a function from the Bordeaux Threads library for multi-threading in Lisp.

Wrap-up questions

Final candidate for Object Lisp 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 Object Lisp application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

What is the Common Lisp Object System (CLOS) and what features does it provide?
The Common Lisp Object System (CLOS) is a powerful, dynamic object system that is part of the Common Lisp language. It provides features such as multiple inheritance, multimethods, generic functions, and method combinations.
How would you define a class in Lisp using CLOS?
In Lisp, classes are defined using the DEFCLASS macro. For example, to define a class named 'person' with two slots 'name' and 'age', you would write: (defclass person () ((name :initarg :name :accessor name) (age :initarg :age :accessor age)))
What are generic functions and methods in CLOS?
In CLOS, a generic function is a function that is defined for many different classes of objects. A method is a specific implementation of a generic function for a particular class or classes of objects.

Object Lisp application related

Product Perfect's Object Lisp development capabilities

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