Data Types

Data types are a collection of “things”. For example, the data type Integer contains, as you’d expect, the integers that you’ve learned from maths:

You can define your own data types. For example:

data Size = Big | Small

Note that the names of data types always begin with a capital letter.

These are the data types you encounter in your assignment: enumerated, product, recursive.

The following types have been copied from your assignment, identify what kind of types they are (i.e enumerated, product or recursive):

data List a = Empty | Entry a (List a)

data Coord = C Integer Integer

data Direction = R | U | L | D

data Tile = Wall | Ground | Storage | Box | Blank

data SSState world = StartScreen | Running world

And now for an exercise copied and pasted from your week 4 lab (part of your assignment!) Define a data type State that captures the state of the game. It should have just one data constructor St that constructs a product of the following types:

  • The current coordinate position of the player, who moves throughout the maze: Coord.
  • The direction the player is facing (i.e., right, up, left or down): Direction.
  • The current coordinate positions of all boxes, as a list: (List Coord).

Is this an enumerated type, product type or recursive type?