Hiring guide for Cool (programming language) Engineers

Cool (programming language) Developer Hiring Guide

Cool (Classroom Object Oriented Language) is a statically-typed, object-oriented programming language designed as a tool for teaching the fundamental concepts of computer programming and software design. It was developed by Alexander Aiken at Stanford University in California. Cool has many features commonly found in modern programming languages, including objects, static typing, and automatic memory management. The primary goal of Cool is to be simple enough for students to understand quickly but powerful enough to illustrate key concepts of object-oriented languages. The syntax and semantics are similar to those of Java or C++, making it easier for students who have learned these languages before. Cool programs are translated into an intermediate language that can be executed on the Cool Runtime Environment (CRE). This allows students to focus on learning the principles behind writing code without worrying about low-level details such as memory management or machine-specific characteristics. One unique feature about Cool is its support for inheritance - a key concept in object-oriented programming where one class can inherit properties from another class. This makes it an excellent choice for teaching this important principle. Despite being primarily used as an educational tool, Cool also supports more advanced features like garbage collection and type checking which make it suitable even beyond classroom use.

Ask the right questions secure the right Cool (programming language) talent among an increasingly shrinking pool of talent.

First 20 minutes

General Cool (programming language) app knowledge and experience

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

What are the main features of the Cool programming language?
Cool has a static type system, automatic memory management, and a rich set of control structures, including conditionals, loops, and exception handling. It supports object-oriented programming with classes and inheritance.
How would you declare a class in Cool?
In Cool, a class is declared using the 'class' keyword followed by the class name, an optional extends clause for inheritance, and a block containing field and method declarations. For example: 'class MyClass extends ParentClass { ... }'.
What is the purpose of the 'self' keyword in Cool?
'self' is a special keyword in Cool that refers to the current object. It's similar to 'this' in Java or C++.
Describe the difference between 'let' and 'in' in Cool.
'let' is used to declare and initialize a new variable, while 'in' is used to denote the scope where this new variable is valid. For example, 'let x:Int in { ... }' declares an integer variable x and the following block is where x is valid.
How would you handle exceptions in Cool?
Cool provides a 'try-catch' mechanism for exception handling. You can catch specific exceptions and handle them in the 'catch' block, or catch all exceptions with a generic catch block.
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What you’re looking for early on

Has the candidate demonstrated a solid understanding of Cool programming language?
Did the candidate show problem-solving skills during the interview?
Does the candidate have experience with projects similar to what your company is working on?
Did the candidate display good communication skills?

Next 20 minutes

Specific Cool (programming language) 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 are the rules for method overriding in Cool?
In Cool, a subclass can override a method from its superclass. The overriding method must have the same name and parameter types as the method in the superclass, and its return type must be a subtype of the return type of the overridden method.
How would you implement multiple inheritance in Cool?
Cool does not support multiple inheritance directly. However, you can simulate multiple inheritance using interfaces or mixin classes.
What is the difference between static and dynamic typing in Cool?
Cool is a statically typed language, which means type checking is performed at compile time. This is different from dynamically typed languages where type checking is performed at runtime.
How would you create an abstract class in Cool?
Cool does not support abstract classes directly. However, you can simulate an abstract class by creating a class with some methods that have no implementation and must be overridden by subclasses.
What is the purpose of the 'new' keyword in Cool?
The 'new' keyword in Cool is used to create a new instance of a class. For example, 'new MyClass()' creates a new instance of MyClass.
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The ideal back-end app developer

What you’re looking to see on the Cool (programming language) engineer at this point.

At this point, a skilled Cool (programming language) engineer should demonstrate strong problem-solving abilities, proficiency in Cool (programming language) 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 Cool (programming language).

What does this simple Cool code do?
class Main inherits IO {
  main(): Object {
    out_string("Hello, World!\n");
This code defines a Main class with a main method. The main method prints the string 'Hello, World!' followed by the integer 42.
What will be the output of the following Cool code?
class Main inherits IO {
  main(): Object {
    out_string("The answer is: ").out_int(21 * 2);
The output of this code will be 'The answer is: 42'. The code multiplies 21 by 2 and then prints the result.
What does the following Cool code do?
class Array {
  elements: Int[10];
  init(): Array {
    let i: Int <- 0 in
    while i < 10 loop
      elements[i] <- i * i;
      i <- i + 1;
This code defines an Array class with an array of 10 integers. The init method initializes the array such that each element at index i is the square of i.
What does the following Cool code do?
class Main inherits IO {
  main(): Object {
    out_string((new A).foo);
class A {
  foo: String <- "bar";
This code defines two classes, Main and A. The main method of the Main class creates a new instance of class A and prints the value of its foo attribute, which is 'bar'.

Wrap-up questions

Final candidate for Cool (programming language) 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 Cool (programming language) application deployments. Inquire about their experience in handling system failures and their approach to debugging and troubleshooting.

Describe the difference between '=' and '<-' in Cool.
'=' is used for comparison, while '<-' is used for assignment. For example, 'if x = y then ...' checks if x and y are equal, while 'x <- y' assigns the value of y to x.
How would you implement polymorphism in Cool?
Polymorphism in Cool can be achieved through method overriding and dynamic dispatch. When a method is invoked on an object, the actual method to execute is determined by the runtime type of the object.
What are the rules for type casting in Cool?
In Cool, you can cast an object to a superclass or subclass type using the 'as' keyword. However, the cast is checked at runtime and will fail if the object is not actually an instance of the target type.

Cool (programming language) application related

Product Perfect's Cool (programming language) development capabilities

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