Instructions

In this exercise you will be implementing a simulation of encounters. This will familiarise you with the basics of multiple dispatch, Julia's main paradigm.

In general, encounters involve one entity a meeting another entity b and reacting to it.

At first, we will simulate what happens when cats and dogs meet.

1. Define custom types

First add an abstract type Pet.

Then define types Cat and Dog as subtypes of Pet. Each has a single field name.

2. Get the name of the pet.

Implement a function name() which returns the name of a pet.

3. Define what happens when cats and dogs meet

Implement meets() methods for the following encounters:

• When two dogs meet, they sniff each other.
• When a cat meets a dog, it hisses at the dog.
• When a dog meets a cat, it chases the cat.
• When two cats meet, they slink.

4. Define an encounter between two entities.

Implement the encounter() function with one method, to report what happens when two named entities meet.

5. Define a fallback reaction for encounters between pets

What happens if they encounter a different pet on their walk, like a horse?

• If a pet meets another pet that it doesn't recognize, it is cautious.

6. Define a fallback if a pet encounters something it doesn't know

There are many other things that pets may encounter that aren't pets: cars, humans, plants, natural disasters, asteroids… What happens then?

• If a pet meets something it has never seen before, it runs away.

7. Define a generic fallback

There are many other encounters that could occur in our simulation. A car meets a dog, two electrons encounter each other and interact…

It is impossible to cover all encounters in advance, therefore we will implement a generic fallback.

• If two unknown things or beings encounter each other, nothing happens.