Class 13: Loopy Recursive Functions

cs1120: Introduction to Computing
Explorations in Language, Logic, and Machine
University of Virginia, Spring 2016

http://xplorecs.org/class13

Class 13:
Loops and Recursive Functions
Hamming Distance
Edit Distance
Copying Lists

Transcript

1. Class 13: Loopy Recursive Functions Introduction to Computing: Explorations in Language, Logic, and Machines cs1120 Spring 2016 David Evans University of Virginia
2. Menu Recursive Functions vs. Loops Hamming Distance Edit Distance Copying Lists (Flattening!) Practice programming with lists and recursive functions!
5. Warning: Blue Belt Version!
6. Which is “Best”?
8. …
9. Why is Python so bad at recursion?
10. “If you want a short answer, it’s simply unpythonic.” Guido van Rossum (Python’s Benevolent Dictator for Life) (blog post on Tail Recursion Elimination)
11. Why You Should be Comfortable with Recursive Definitions (even if they are never really necessary and not encouraged in Python): 1. Learning to think, not learning to program. Recursive definitions are great tools for thinking. 2. Learning to program, not learning to Python. Ways to describe computations, not just what works best in Python. 3. Even in Python, more complex programs that operate on recursive data are best as recursive functions.
12. Why are we learning Python if it is so bad at recursion?
13. Levenshtein Distance edit_distance(a, b) = The minimum number of insert, delete, and mutate operations needed to transform a into b. Does it matter if the definition is a into b or b into a?
14. Levenshtein Distance edit_distance(a, b) = base case:
16. Shorter…is it better?
17. Copying Lists
19. Charge Return Project 2: – Gold star: Congratulations! Orange Belt – Green star: Read notes for how to earn Orange Belt – No star: make sure to talk to or email me (if you haven’t already)