Implement new Concept Exercise: mutation

[ErikSchierboom]

This issue describes how to implement the mutation 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 Mutation in F#.

Learning objectives

• Know how mutation works in F#.
• Know how to define a variable (mutable binding).
• Know how to work with reference cells.
• Know how to update mutable values.
• Know when to use mutability.

Out of scope

• How the compiler sometimes translates functional code to mutation.

Concepts

The Concepts this exercise unlocks are:

• mutation: know how mutation works in F#; know how to define a variable (mutable binding); know how to work with reference cells; know how to update mutable values; know when to use mutability.

Prerequisites

This exercise's prerequisites Concepts are:

• generic-types: know what a generic type is.
• records: know how to work with records.

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

Resources to refer to

Hints

• Variables: how to define variables.
• Reference cells: how to work with reference cells.

After

• Variables: how to define variables.
• Reference cells: how to work with reference cells.

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.