Implement new Concept Exercise: fields

[ErikSchierboom]

This issue describes how to implement the fields concept exercise for the F# track.

Getting started

Please please please read the docs before starting. Posting PRs without reading these docs will be a lot more frustrating for you during the review cycle, and exhaust Exercism's maintainers' time. So, before diving into the implementation, please read up on the following documents:

• The features of v3.
• Rationale for v3.
• What are concept exercise and how they are structured?

Please also watch the following video:

• The Anatomy of a Concept Exercise.

Goal

The goal of this exercise is to teach the student the basics of the Concept of Fields in F#.

Learning objectives

• Know what fields are.
• Know how to define immutable fields.
• Know how to define mutable fields.
• Know what shadowing is.
• Know how to shadow a binding.

Out of scope

• Static fields.
• Properties.
• Additional constructors.
• do bindings.

Concepts

The Concepts this exercise unlocks are:

• fields: know what fields are; know what the difference is between fields and records and when to use which; know what encapsulation is; know how to create an object;
  know how to define methods.
• shadowing: know what shadowing is; know how to shadow a binding.

Prerequisites

This exercise's prerequisites Concepts are:

• classes: know how to define a class.
• mutation: know how to create mutable bindings.
• unit: know about the unit type.

Any data types used in this exercise (e.g. strings or integers) should also be added as prerequisites.

Resources to refer to

Hints

• Fields: how to define mutable and immutable fields.
• Shadowing: how to use shadowing to mutate immutable constructor parameters.

After

• Fields: how to define mutable and immutable fields.
• Shadowing: how to use shadowing to mutate immutable constructor parameters.

Representer

This exercise does not require any specific representation logic to be added to the representer.

Analyzer

This exercise does not require any specific logic to be added to the analyzer.

Implementing

To implement this exercise, please follow these instructions.

Help

If you have any questions while implementing the exercise, please post the questions as comments in this issue.