![18
Recursion vs. Iteration
Can recursively call function on list:
let rec sumList lst =
match lst with
| [] -> 0 //Matches empty list
| hd :: tl -> hd + sumList tl ;;
let l = [1..100];;
sumList l;; // 5050](https://image.slidesharecdn.com/gentleintrotofpdcode-170711163704/85/Gentle-Introduction-To-Funcitonal-Programming-Detroit-Code-18-320.jpg)
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Gentle Introduction To Funcitonal Programming - Detroit.Code
- 1. A Gentle Introduction To The Basics Of Functional Programming Onorio Catenacci, IT Trainer United Shore, Troy, MI
- 2. 2 Agenda Dispelling Myths About FP What is Immutability and Why Should You Care? What Are First-Class Functions? Built-in Regular Expressions Recursion vs. Iteration Summary/Review
- 3. 3 Myths About FP Adopting FP Ideas Means You Must Stop Writing OO Code
- 4. 4 Myths About FP Adopting FP Ideas Means You Must Stop Writing OO Code Learning a New Approach Means Discarding The Old One.
- 5. 5 Myths About FP Adopting FP Ideas Means You Must Stop Writing OO Code FP Doesnt Have Classes.
- 6. 6 Myths About FP Adopting FP Ideas Means You Must Stop Writing OO Code You Cant Write FP in Java or C#.
- 7. 7 Myths About FP FP is a New Idea
- 8. 8 Myths About FP You Can Only Write FP in an FP Language
- 9. 9 Myths About FP OO is More Natural
- 10. 10 Immutability What is Immutability and Why Should You Care i++;
- 11. 11 Immutability Languages Mostly Help Or Hinder Us In Terms Of The Defaults! Developers Wont Fight Language Defaults!
- 12. 12 First Class Functions What Do We Mean When We Say Function In FP? let square n = n * n
- 13. 13 First Class Functions What is a First Class Function?
- 14. 14 First Class Functions What is a First Class Function? First Class Functions Serve Analogous Purpose to Polymorphism in OO.
- 15. 15 First Class Functions let iseven n = n % 2 == 0 let isodd n = not iseven n let EvenIsDifferent fnForEven fnForOdd n = if iseven n then fnForEven n else fnForOdd n
- 16. 16 Built-In Regular Expressions let regexDemo fn value = match (fn value) with | true -> "It's true" | false -> "Nope it's false";; regexDemo iseven 3;; // val it : string = "Nope it's false"
- 17. 17 Recursion vs. Iteration By Default Values Are Immutable In FP Cannot mutate index into list for i = 0; i++; i < length(list) //Not allowed!
- 18. 18 Recursion vs. Iteration Can recursively call function on list: let rec sumList lst = match lst with | [] -> 0 //Matches empty list | hd :: tl -> hd + sumList tl ;; let l = [1..100];; sumList l;; // 5050
- 19. 19 Summary/Review FP doesnt mean Discard OO FP has default immutability FP has 1st class functions FP emphasizes recursion over iteration.
- 20. 20 Feedback Twitter: @OldDutchCap E-mail: catenacci@ieee.org Also please fill out survey: https://tinyurl.com/dcode-fp Survey is anonymous.
Editor's Notes
- #3: Dispelling myths about FP Whats immutability and why does it matter? Whats a first class function? Built-in regular expressions Recursion vs. iteration Summary/review
- #4: Someone seems to have gotten the mistaken notion that adopting FP means dropping OO; nothing could be further from the truth. Lets look at a few of the assumptions underlying that: 1.) Learning a new approach means abandoning an old approach. 2.) FP doesnt have classes
- #5: Someone seems to have gotten the mistaken notion that adopting FP means dropping OO; nothing could be further from the truth. Lets look at a few of the assumptions underlying that: 1.) Learning a new approach means abandoning an old approach. 2.) FP doesnt have classes
- #6: Someone seems to have gotten the mistaken notion that adopting FP means dropping OO; nothing could be further from the truth. Lets look at a few of the assumptions underlying that: 1.) Learning a new approach means abandoning an old approach. 2.) FP doesnt have classes
- #7: Someone seems to have gotten the mistaken notion that adopting FP means dropping OO; nothing could be further from the truth. Lets look at a few of the assumptions underlying that: 1.) Learning a new approach means abandoning an old approach. 2.) FP doesnt have classes