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Ask the right questions to secure the right F* talent among an increasingly shrinking pool of talent.
The F* (F Star) computer programming language is a sophisticated, statically-typed functional programming language developed by Microsoft Research. It was designed for program verification, enabling developers to write annotations expressing properties they want their programs to have. The F* type-checker aims to prove these properties via an automated theorem prover. This language is used in several Microsoft projects, including Project Everest, which aims to build a verified HTTPS stack. Its development and application are documented in numerous research papers published by Microsoft Research.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
F* includes basic data types like integers, booleans, strings, and more complex ones like lists, options, and references.
F* has a mechanism known as the 'effect system'. This allows programmers to mark functions with their side-effects, which are then checked during the verification process.
The main difference is that F* has a built-in mechanism for program verification. It allows programmers to write specifications and prove them as part of the program.
F* provides strong type-checking, effect system, and a powerful system for defining and proving properties about programs.
F* is a functional programming language aimed at program verification. It puts forth a mechanism to define the specification of a program and verify the program against the specification.
This is important because it indicates that the candidate is likely to be motivated and committed to the job.
This is crucial because technology is always evolving, and developers need to be able to keep up with new trends and tools.
This is important because it shows that the candidate is already familiar with the tools they'll be using in the role.
This is necessary because effective communication is key in a team environment.
This is important because programming often involves finding solutions to complex problems.
This is crucial because F* is a functional programming language that requires a unique set of skills and understanding.
The next 20 minutes of the interview should attempt to focus more specifically on the development questions used, and the level of depth and skill the engineer possesses.
F* is not as mature or widely used as other languages, so it may lack libraries and tooling. Also, writing specifications and proofs can be time-consuming.
In such cases, you can provide additional hints or lemmas to help Z3. If that's not possible, you can also use a manual proof mode to guide the proof.
F* uses the Z3 solver to automatically prove properties about programs. It translates the verification conditions into logical formulas that Z3 can solve.
Dependent types can be used to express precise properties about a program. For example, you can define a type of sorted lists and then write functions that only operate on sorted lists.
Dependent types in F* allow types to depend on values, which provides a way to express more precise types and invariants. Traditional type systems usually don't have this feature.
A skilled F* engineer should demonstrate proficiency in formal verification, functional programming, and knowledge of F* syntax and semantics. Red flags include lack of problem-solving skills, inability to explain complex concepts clearly, or unfamiliarity with the F* language and its applications.
let square x = x * xlet x = 5
let y = 3
printfn "%d" (x % y)let list1 = [1;2;3;4;5]
let list2 = List.map (fun x -> x * 2) list1let mutable counter = 0
[]
do while counter < 5 do
counter <- counter + 1 type Circle(radius:float) =
member this.Area = Math.PI * radius * radiuslet rec factorial n =
if n = 0 then 1 else n * factorial (n - 1)The final few interview questions for a F* candidate should typically focus on a combination of technical skills, personal goals, growth potential, team dynamics, and company culture.
F* can be used to verify critical parts of the system, such as cryptographic algorithms, to ensure they are free of bugs. This can significantly improve the system's security.
The main challenges are the time required to write specifications and proofs, and the need to train developers in F* and formal verification.
F* has a 'div' effect for non-terminating computations. You can use this effect to explicitly mark non-terminating functions.
Total functions in F* are guaranteed to terminate and not throw exceptions, while partial functions may not terminate or throw exceptions. F* checks totality by default.
First, I would define the specification of the algorithm using F*'s type system. Then, I would write the algorithm and use F*'s verification mechanism to prove that it meets the specification.
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