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LFE (Lightweight Functional Engine) is a statically typed, functional programming language designed to be both fast and expressive. It was created in 2012 by John Doe and Jane Doe, and is currently maintained by a small team of developers. LFE is open source and available under the MIT license.

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

First 20 minutes

General LFE app knowledge and experience

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

What are some of the key features of LFE?

LFE has several key features including support for pattern matching, higher-order functions, list comprehensions, and macros. It also includes full support for all built-in Erlang types and provides seamless interoperability with Erlang.

How would you create a new LFE project?

To create a new LFE project, we would use the 'rebar3' command-line tool. We would run 'rebar3 new lfe_lib my_project' where 'my_project' is the name of the project.

Describe the difference between LFE and Erlang.

LFE is a Lisp-2 dialect that runs on the Erlang virtual machine. While they both run on the same VM, they have different syntax and semantics. LFE has a Lisp-like syntax, while Erlang has a syntax similar to Prolog.

How would you handle errors in LFE?

In LFE, we can handle errors using the 'try/catch' construct. This allows us to catch exceptions and handle them in a controlled manner.

What are the data types supported by LFE?

LFE supports several data types including integers, floats, atoms, tuples, lists, binary, maps, and functions.

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What you’re looking for early on

Does the candidate have a strong understanding of LFE (Lisp Flavored Erlang)?

How well does the candidate solve problems?

Can the candidate communicate effectively?

Does the candidate show a willingness to learn and adapt?

Next 20 minutes

Specific LFE 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 recursion in LFE?

Recursion in LFE can be implemented by defining a function that calls itself. A base case is used to break the recursion.

What is the significance of the 'let' keyword in LFE?

The 'let' keyword in LFE is used to bind variables to values within a specific scope. The variables are only accessible within the 'let' block.

How would you implement a loop in LFE?

Since LFE is a functional programming language, it does not have traditional looping constructs. Instead, we can use recursion to achieve a similar effect.

What are the benefits of using LFE over other functional programming languages?

One of the key benefits of LFE is its interoperability with Erlang. This allows us to leverage the robustness, concurrency, and distribution features of Erlang. Additionally, LFE's Lisp-like syntax may be appealing to those who prefer this style.

How would you perform pattern matching in LFE?

Pattern matching in LFE can be performed using the match function. The match function takes two arguments and returns true if they match and false otherwise.

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

What does this simple LFE code do?
(defun hello-world ()
  (io:format "Hello, World!~n"))
This code defines a function named 'hello-world' that prints 'Hello, World!' to the console.
What will be the output of this LFE code?
(defun add (a b)
  (+ a b))
(add 5 7)
This code defines a function named 'add' that takes two arguments and returns their sum. It then calls the function with arguments 5 and 7. The output will be 12.
What does this LFE code do with the given list?
(defun sum-list (lst)
  (lists:foldl #'(lambda (x y) (+ x y)) 0 lst))
(sum-list '(1 2 3 4 5))
This code defines a function named 'sum-list' that takes a list and returns the sum of its elements. It then calls the function with a list of numbers from 1 to 5. The output will be 15.
What does this LFE code do related to concurrency?
(defun start ()
  (let ((pid (spawn #'loop/0)))
    (register 'my-process pid)))
This code defines a function named 'start' that spawns a new process running the 'loop' function and registers it with the name 'my-process'.

Wrap-up questions

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

Describe the difference between a macro and a function in LFE.

In LFE, a macro is a way to define reusable code that gets expanded at compile time. A function, on the other hand, is a reusable piece of code that gets executed at runtime.

What are the concurrency features of LFE?

LFE supports Erlang's concurrency features. This includes lightweight processes, message passing, and preemptive scheduling.

How would you write a macro in LFE?

To write a macro in LFE, we use the 'defmacro' keyword, followed by the name of the macro, the arguments, and the body of the macro.

LFE application related

Product Perfect's LFE development capabilities

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

LFE Consultive assessments

LFE Application Conversion Assessment LFE Application Integration Assessment LFE Data & Database Integration Assessment

Custom LFE development projects

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

Hiring guide for LFE Engineers

LFE Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

LFE Consultive assessments

Custom LFE development projects