Computer Science for Beginners

Lesson 2: Functions

Lesson Date: 2024-06-30

Domain and Range
- Domain: The set of all possible inputs
- Range: The set of all possible outputs
Function Signature
- Name
- Parameter list
Parameters vs Arguments
- Technically, they refer to the same thing, but have slight nuanced differences
- Similar to: Emigrate (from) vs Immigrate (to)
- Functions receive parameters
- Functions are called (or invoked) with arguments
Arity of Functions
- Nullary / Niladic (receives 0 arguments)
- Unary / Monadic (receives 1 argument)
- Binary / Dyadic (receives 2 arguments)
- Ternary / Triadic (receives 3 arguments)
- Quaternary / Tetradic (4)
- Quinary / Pentadic (5)
- Senary / Hexadic (6)
- Septenary / Hebdomadic (7)
- Octonary / Ogdoadic (8)
- Nonary / Enneadic (9)
- Denary / Decenary
- n-ary
- Variadic (varying arguments)
Composition of functions
- Functions that call other functions
- Single-responsibility principle
  - One function should do one thing
Abstraction & Encapsulation
- Things we use in our daily lives without understanding how they work "under the hood"
  - Cars
  - Airplanes
Helper Functions
- Break down more complex steps into logical sections
- Think about making a PB&J sandwich... now, making a pizza. Making a pizza requires multiple phases.
- Helpers vs Utilities
  - Not useful standalone (helper functions) vs useful standalone (utility functions)
Recursion
- It is its own helper function
- Base case(s)
- Recursive case(s)
- Subproblems
Recursion Examples
- Video call infinite mirroring

Please sign up for the Python + Javascript track on Exercism:

Notes

Since students should already have GitHub accounts, please sign up for Exercism using GitHub.
Exercism is nice, used by A LOT of people, and has both an online as well as an offline (requires installing software on local computer) option.
Get through as many exercises as you can (at the minimum, try to do 1)
FWIW (for what it's worth), it took me 5 minutes to sign up and complete the first exercise in Python -- most of the time was spent reading the website instructions and understanding its layout -- and 20 seconds to complete the first exercise in JavaScript
Just a friendly reminder that it's not a race or a competition.

General reminders

If you are stuck on anything for 15-30 minutes without a way forward, please post any question(s) in the Slack channel to ask for help!