Hiring guide for Visual Prolog Engineers

Visual Prolog Developer Hiring Guide

Visual Prolog, formerly known as PDC Prolog and Turbo Prolog, is a strongly typed object-oriented variant of the Prolog programming language. It is developed by the Danish company Prolog Development Center that also originally developed Turbo Prolog. Visual Prolog is a powerful tool well suited for deploying artificial intelligence, building industrial strength applications, rapid prototyping and advanced graphical user interfaces. It incorporates features like explicit type declaration requirements, encapsulation and inheritance, making it more similar to languages like C++ and Java than traditional versions of Prolog.

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

First 20 minutes

General Visual Prolog app knowledge and experience

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

How would you define Prolog?
Prolog is a logic programming language associated with artificial intelligence and computational linguistics. It has its roots in first-order logic, a formal logic, and unlike many other programming languages, Prolog is declarative: the program logic is expressed in terms of relations, represented as facts and rules.
What are the key features of Visual Prolog?
Visual Prolog, as a powerful programming language, combines the features of logical, functional and object-oriented programming. It supports building Windows GUI applications, COM objects, ActiveX components, and .NET assemblies.
Describe the difference between facts and rules in Prolog.
Facts in Prolog are basic assertions about some world. They state things that are unconditionally true. On the other hand, rules are conditional truths. They have a head and a body, and can be read as implications.
How would you use recursion in Visual Prolog?
Recursion in Visual Prolog is used to solve problems that can be broken down into smaller, similar problems. A recursive predicate calls itself with a smaller or simpler version of the original problem until it reaches a base case that can be solved directly.
What are the uses of lists in Prolog?
Lists in Prolog are used to group together items that belong to the same category or have some relationship. They are used in various ways, such as representing sequences, sets, or even trees and other complex structures.
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What you’re looking for early on

Does the candidate have a strong understanding of Visual Prolog?
Has the candidate demonstrated problem-solving skills?
Is the candidate able to communicate effectively?
Does the candidate have experience with other programming languages?

Next 20 minutes

Specific Visual Prolog 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.

Describe the difference between cut and fail predicates in Prolog.
The cut predicate in Prolog is used to prune the search tree and commit to the choices made at the point where it appears, whereas the fail predicate is used to force backtracking.
How would you handle exceptions in Visual Prolog?
Visual Prolog provides a try-catch-finally construct for exception handling. When an exception occurs in the try block, control is transferred to the catch block. The finally block is executed regardless of how control leaves the try block.
What are the different data types in Visual Prolog?
Visual Prolog supports several data types including integer, real, string, char, term, list, and various compound types.
Describe the difference between dynamic and static predicates in Prolog.
Dynamic predicates in Prolog can have clauses added or removed during the execution of a program, whereas static predicates cannot be changed during execution.
How would you implement object-oriented programming in Visual Prolog?
Visual Prolog supports object-oriented programming through the use of classes and interfaces. A class encapsulates data and operations on that data, while an interface defines a contract that a class can choose to implement.
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The ideal back-end app developer

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

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

What does this code snippet do in Visual Prolog?
    color = red; green; blue.
paint(red) :- write('Red Paint').
This code defines a domain 'color' with elements red, green, and blue. It also defines a predicate 'paint' that accepts an argument of type color. When the argument is 'red', it writes 'Red Paint' to the output.
What will be the output of this Visual Prolog code?
    run() :-
        X = 5,
        Y = 10,
        Z = Y - X,
This code will output '5'. It defines a predicate 'run' which calculates the value of 'Z' by subtracting 'X' from 'Y' and then writes this value to the output.
What does this Visual Prolog code do?
    sumList([], 0).
    sumList([H|T], Sum) :-
        sumList(T, Sum1),
        Sum = H + Sum1.
This code defines a predicate 'sumList' that calculates the sum of all elements in a list. The first clause defines the base case of an empty list, where the sum is 0. The second clause recursively calls 'sumList' on the tail of the list, then adds the head to the accumulated sum.
What does this Visual Prolog code do?
    start() :-
        thread::create(go, ThreadId, _),
    go() :-
        write('Hello, World!').
This code creates a new thread and runs the 'go' predicate in it, which writes 'Hello, World!' to the output. The 'start' predicate creates the thread and then waits for it to finish.

Wrap-up questions

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

What are the steps to create a GUI application in Visual Prolog?
Creating a GUI application in Visual Prolog involves several steps: defining the GUI layout, creating event handlers for user interactions, and writing the logic for the application.
Describe the difference between depth-first and breadth-first search in Prolog.
Depth-first search in Prolog explores as far as possible along each branch before backtracking, whereas breadth-first search explores all the nodes at the present depth before going to the next level.
How would you optimize a Visual Prolog program?
Optimizing a Visual Prolog program can involve several techniques, such as avoiding unnecessary computations, using the appropriate data structures, and taking advantage of Prolog's built-in predicates.

Visual Prolog application related

Product Perfect's Visual Prolog development capabilities

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