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Caml is a statically-typed, functional programming language developed in the late 1980s at INRIA, a French national research institution. It is part of the ML (Meta Language) family, which also includes languages like Standard ML and Haskell. Caml is particularly noted for its strong type-inference system and pattern-matching capabilities. The language has evolved over time, with its most popular variant being OCaml, which adds object-oriented constructs to the core language. Its design and development have significantly influenced other programming languages such as F# and Scala.

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

First 20 minutes

General Caml app knowledge and experience

The first 20 minutes of the interview should seek to understand the candidate's general background in Caml 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 Caml?

The basic data types in Caml are integers, floating-point numbers, characters, strings, and booleans.

How would you declare a function in Caml?

In Caml, a function can be declared using the 'let' keyword followed by the function name, parameters, and the function body. For example, 'let add x y = x + y'.

Describe the difference between 'let' and 'let rec' in Caml.

'let' is used to bind a name to a value, whereas 'let rec' is used to define a recursive function.

What are algebraic data types in Caml?

Algebraic data types in Caml are composite types that can be either product types (records) or sum types (variants).

How would you implement a binary search tree in Caml?

A binary search tree in Caml can be implemented using a recursive data type and functions for insertion, deletion, and search.

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What you’re looking for early on

Does the candidate have a strong understanding of the Caml language?

Has the candidate demonstrated problem-solving skills?

Is the candidate familiar with the tools and technologies commonly used in Caml development?

Can the candidate communicate effectively about complex technical concepts?

Next 20 minutes

Specific Caml 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 is the purpose of the 'match' keyword in Caml?

The 'match' keyword in Caml is used for pattern matching. It allows you to destructure data types and execute different code based on the pattern.

How would you handle exceptions in Caml?

Exceptions in Caml can be handled using the 'try' and 'with' keywords. You can catch and handle exceptions in the 'with' block.

Describe the difference between '=' and '==' in Caml.

'=' is used for structural equality, which means the values are equal. '==' is used for physical equality, which means the values are identical.

What are first-class functions in Caml?

First-class functions in Caml are functions that can be treated as values. They can be passed as arguments, returned from other functions, and assigned to variables.

How would you use a higher-order function in Caml?

A higher-order function in Caml is a function that takes another function as an argument or returns a function. For example, the 'map' function is a higher-order function.

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

What does this simple Caml code do?
let rec factorial n = if n = 0 then 1 else n * factorial (n-1);;
This code defines a recursive function to calculate the factorial of a number. If the input number is 0, it returns 1. Otherwise, it multiplies the number by the factorial of the number minus one.
What will be the output of the following Caml code?
let rec sum n = if n <= 0 then 0 else n + sum (n-1);; print_int (sum 5);;
The output of this code will be 15. The code defines a recursive function to calculate the sum of all numbers from the input number down to 1. It then calls this function with the argument 5.
What does this Caml code do with an array?
let array_sum arr = Array.fold_left (+) 0 arr;; print_int (array_sum [|1; 2; 3; 4; 5|]);;
This code defines a function to calculate the sum of all elements in an array. It then calls this function with an array of integers from 1 to 5. The output will be the sum of these numbers, which is 15.
What does this Caml code do related to threading?
let rec fib n = if n < 2 then n else fib (n-1) + fib (n-2);; let _ = Thread.create fib 10;;
This code defines a recursive function to calculate the Fibonacci number at a given position. It then creates a new thread to calculate the 10th Fibonacci number. The result is not printed, so there will be no output.

Wrap-up questions

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

Describe the difference between a tuple and a list in Caml.

A tuple in Caml is a fixed-size collection of values, possibly of different types. A list is a variable-size collection of values, all of the same type.

What is currying in Caml?

Currying in Caml is the process of transforming a function that takes multiple arguments into a function that takes one argument and returns another function.

How would you use modules in Caml?

Modules in Caml are used to group related definitions. You can define a module using the 'module' keyword and use its definitions with the '.' operator.

Caml application related

Product Perfect's Caml development capabilities

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

Caml Consultive assessments

Caml Application Conversion Assessment Caml Application Integration Assessment Caml Data & Database Integration Assessment

Custom Caml development projects

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

Hiring guide for Caml Engineers

Caml Developer Hiring Guide

What you’re looking for early on

The ideal back-end app developer

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

Caml Consultive assessments

Custom Caml development projects