Types & Classes

Classes

Let's lead with an example. Suppose we want to implement booleans:

class Bool:

True

False

This code defines two new values we can use - True and False.

Type classes

The above values aren't super useful right now, we can't do anything with them. Suppose we wanted an equals function to compare boolean values. We would want a function like:

def equals(firstBoolean, secondBoolean)

In fact, we probably want this function for a lot of other classes like ints, lists, JSON objects, ...

That's where type classes come in:

type Equal:

def equals(self, self)

This defines a template that classes can base their equals methods off of. If a class implements this equals function, we know that we can compare two variables of that class. This function is actually called when you use the == operator in Monty.

The self is a special keyword that indicates which parameter to use for looking up the implementation of equals.

Instances

Ok so how do we actually implement this function for a class? With instances!

instance Bool of Equal:

def equals(True, True):

return True

def equals(False, False):

return True

def equals(_, _):

return False