Lesson 29 of 55
10 mins readAlgebraic Data Types (data ADT)
In Plain English
Algebraic Data Types (ADTs) allow defining rich custom domain types. Combine alternative variants (sum types with |) and composite fields (product types).
Deep Dive: How It Works
Sum Types (Enums/Variants): data TrafficLight = Red | Yellow | Green deriving (Show, Eq).
Product Types with Arguments: data Shape = Circle Double | Rectangle Double Double.
Automatic Deriving: deriving (Show, Eq, Ord) instructs GHC to generate standard typeclass instances automatically.
Core Rules to Remember
Sum & Product Types: Model domain states with mathematical precision.
deriving (Show, Eq): Automatically generate string representation and equality comparison.
Live Interactive Example
Hit Run Code to see it liveGeometric Shapes ADT
Python 3.12
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Output Console
Click "Run Code" to view the rendered output.
How it works: area uses pattern matching to deconstruct Circle and Rectangle constructors.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Define Direction ADT
- Define `data Direction = North | South | East | West deriving (Show, Eq)`.
- Print `"Direction: "` followed by `show North`.
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Sandbox Output
Click "Run & Check" to test your solution.
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