Product Perfect

Agda is a dependently typed functional programming language, originally developed by Ulf Norell at Chalmers University of Technology, Sweden. It is designed to be a platform for research in type theory, dependent types, and interactive theorem proving. Agda is named after Agda Åman, the first woman to receive a Ph.D. in computer science in Sweden. The language is influenced by other functional programming languages such as Haskell and ML. It is open-source and its development is hosted on GitHub.

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

First 20 minutes

General Agda app knowledge and experience

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

How would you define Agda?

Agda is a dependently typed functional programming language that has been designed to be a language for mathematics, software verification, and general-purpose programming.

What are the main features of Agda?

Agda is a dependently typed language, which means that types can depend on values. It also supports interactive theorem proving, inductive and coinductive types, and has a module system.

Describe the difference between Agda and other functional programming languages.

The main difference is that Agda is a dependently typed language, which means that types can depend on values. This allows for more expressive types and more powerful type checking. Agda also supports interactive theorem proving, which is not common in other functional programming languages.

How would you define a dependent type in Agda?

A dependent type in Agda is a type that depends on a value. This allows for more expressive types and more powerful type checking.

What are inductive and coinductive types in Agda?

Inductive types in Agda are types that are defined by a finite set of constructors. Coinductive types, on the other hand, are types that are defined by a potentially infinite set of observations.

The hiring guide has been successfully sent to your email address.

Oops! Something went wrong while submitting the form.

What you’re looking for early on

Does the candidate have a strong understanding of Agda?

Can the candidate demonstrate problem-solving skills?

Is the candidate able to communicate effectively?

Does the candidate have experience with other functional programming languages?

Next 20 minutes

Specific Agda 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 use interactive theorem proving in Agda?

Interactive theorem proving in Agda is done by writing a program that represents the proof of the theorem. The Agda type checker then verifies the correctness of the proof.

Describe the difference between dependent types and regular types in Agda.

The main difference is that dependent types can depend on values, while regular types cannot. This allows for more expressive types and more powerful type checking in Agda.

How would you define a module in Agda?

A module in Agda is a way to group related definitions. It can contain types, functions, and other modules.

What are the benefits of using Agda for software verification?

The main benefit of using Agda for software verification is that it allows for formal verification of the correctness of the software. This is done by writing a program that represents the proof of the correctness of the software, which is then verified by the Agda type checker.

How would you use coinductive types in Agda?

Coinductive types in Agda are used to represent potentially infinite data structures. They are defined by a potentially infinite set of observations, and can be used to model things like streams and infinite lists.

The hiring guide has been successfully sent to your email address.

Oops! Something went wrong while submitting the form.

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

What does this simple Agda function do?
id : ? {A : Set} ? A ? A
id x = x
This is an identity function. It takes an argument of any type A and returns the same value.
What does the following Agda code do?
_+_ : N ? N ? N
zero + n = n
(suc m) + n = suc (m + n)
This code defines a function for addition on natural numbers. It is defined recursively: the sum of zero and any number n is n, and the sum of the successor of m (suc m) and n is the successor of the sum of m and n.
What does this Agda code do?
filter : ? {A : Set} ? (A ? Bool) ? List A ? List A
filter p [] = []
filter p (x ? xs) with p x
... | true = x ? filter p xs
... | false = filter p xs
This code defines a filter function for lists. The function takes a predicate and a list, and returns a new list containing only the elements of the original list that satisfy the predicate.
What does this Agda code do?
mutual
data _|_ (m n : N) : Set where
  zero|n : zero | n
  suc|n : ? {m'} ? suc m' | n ? m | suc n

_/_ : N ? N ? N
m / n with m |? n
... | yes p = zero
... | no ¬p with suc (m / n)
... | q = suc q
This code defines a division function for natural numbers. It uses a mutual block to define both a relation that represents divisibility and the division function itself. The division function uses the divisibility relation to decide whether to return zero or the successor of the result of a recursive call.

Wrap-up questions

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

Describe the difference between inductive and coinductive types in Agda.

The main difference is that inductive types are defined by a finite set of constructors, while coinductive types are defined by a potentially infinite set of observations. This makes inductive types suitable for representing finite data structures, and coinductive types suitable for representing potentially infinite data structures.

How would you use dependent types for software verification in Agda?

Dependent types can be used for software verification in Agda by encoding the properties of the software in the types. The Agda type checker then verifies that the software satisfies these properties.

What are the challenges of using Agda for general-purpose programming?

One of the main challenges of using Agda for general-purpose programming is that it requires a different mindset compared to traditional programming languages. In particular, programming in Agda often involves proving properties about the program, which can be more time-consuming and difficult than traditional programming.

Agda application related

Product Perfect's Agda development capabilities

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

Agda Consultive assessments

Agda Application Conversion Assessment Agda Application Integration Assessment Agda Data & Database Integration Assessment

Custom Agda development projects

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

Hiring guide for Agda Engineers

Agda Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

Agda Consultive assessments

Custom Agda development projects