Lesson 13 of 55
9 mins readPython Function Signatures & Referential Transparency
In Plain English
Functions are pure mathematical mappings in Haskell. Declare explicit type signatures with :: and -> arrows. Because functions are pure, any function call can be replaced with its value (referential transparency).
Deep Dive: How It Works
Type Signatures: add :: Int -> Int -> Int means a function taking an Int and returning a function taking an Int and returning an Int.
Referential Transparency: An expression can be substituted with its resulting value anywhere without altering program behavior.
No Hidden State: Functions cannot modify hidden state or rely on mutable memory.
Core Rules to Remember
Explicit Type Signatures (::): Document and enforce types using :: and -> arrows.
Referential Transparency: Code is predictable and trivially testable because functions produce no side effects.
Live Interactive Example
Hit Run Code to see it liveExplicit Function Signatures
Python 3.12
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Output Console
Click "Run Code" to view the rendered output.
How it works: addThree takes three Ints and returns their sum as an Int.
Your Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Micro Exercise
Define Multiply Three Numbers
- Define `multThree :: Int -> Int -> Int -> Int` and implement `multThree a b c = a * b * c`.
- Print `"Result: "` followed by `show (multThree 2 3 4)`.
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Sandbox Output
Click "Run & Check" to test your solution.
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