Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Finding Happiness in Functional Programming
Search
Brandon Williams
October 01, 2016
Programming
0
610
Finding Happiness in Functional Programming
Video:
https://www.youtube.com/watch?v=A0VaIKK2ijM
Brandon Williams
October 01, 2016
Tweet
Share
More Decks by Brandon Williams
See All by Brandon Williams
Server-Side Swift from Scratch
mbrandonw
4
1.8k
Playground Driven Development
mbrandonw
0
330
Anything You Can Do I Can Do Better
mbrandonw
1
120
The Two Sides of Testing
mbrandonw
1
150
Other Decks in Programming
See All in Programming
2分台で1500examples完走!爆速CIを支える環境構築術 - Kaigi on Rails 2025
falcon8823
3
3.6k
開発生産性を上げるための生成AI活用術
starfish719
3
970
CSC305 Lecture 05
javiergs
PRO
0
210
Flutterで分数(Fraction)を表示する方法
koukimiura
0
130
Catch Up: Go Style Guide Update
andpad
0
230
組込みだけじゃない!TinyGo で始める無料クラウド開発入門
otakakot
0
260
After go func(): Goroutines Through a Beginner’s Eye
97vaibhav
0
390
GraphQL×Railsアプリのデータベース負荷分散 - 月間3,000万人利用サービスを無停止で
koxya
1
1.3k
タスクの特性や不確実性に応じた最適な作業スタイルの選択(ペアプロ・モブプロ・ソロプロ)と実践 / Optimal Work Style Selection: Pair, Mob, or Solo Programming.
honyanya
3
170
CSC509 Lecture 06
javiergs
PRO
0
260
技術的負債の正体を知って向き合う / Facing Technical Debt
irof
0
170
他言語経験者が Golangci-lint を最初のコーディングメンターにした話 / How Golangci-lint Became My First Coding Mentor: A Story from a Polyglot Programmer
uma31
0
100
Featured
See All Featured
Let's Do A Bunch of Simple Stuff to Make Websites Faster
chriscoyier
508
140k
Side Projects
sachag
455
43k
The Cost Of JavaScript in 2023
addyosmani
55
9k
Automating Front-end Workflow
addyosmani
1371
200k
What's in a price? How to price your products and services
michaelherold
246
12k
Visualizing Your Data: Incorporating Mongo into Loggly Infrastructure
mongodb
48
9.7k
Producing Creativity
orderedlist
PRO
347
40k
Agile that works and the tools we love
rasmusluckow
331
21k
Reflections from 52 weeks, 52 projects
jeffersonlam
353
21k
Building Applications with DynamoDB
mza
96
6.7k
How STYLIGHT went responsive
nonsquared
100
5.8k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
37
2.6k
Transcript
Finding Happiness in Functional Programming
None
Principles that we benefited from
Separation of effects from purity
Isolation of side-effects An expression is said to have a
side-effect if its execution makes an observable change to the outside world.
Isolation of side-effects self.titleLabel.text = user.name
Isolation of side-effects func update(text: String, forLabel: UILabel) { label.text
= text } update(text: user.name, forLabel: self.titleLabel)
Isolation of side-effects self.loginButton.enabled = !self.userTextField.text.isEmpty && !self.passwordTextField.text.isEmpty
Isolation of side-effects func updateLoginButtonEnabled() { self.loginButton.enabled = !self.userTextField.text.isEmpty &&
!self.passwordTextField.text.isEmpty } func emailChanged() { self.updateLoginButtonEnabled() } func passwordChanged() { self.updateLoginButtonEnabled() }
Isolation of side-effects // Pure, functional world let emailChanged: Signal<String,
NoError> let passwordChanged: Signal<String, NoError> let loginButtonEnabled = combineLatest(emailChanged, passwordChanged) .map { !$0.isEmpty && !$1.isEmpty } // Side-effect world loginButtonEnabled.observeNext { [weak self] in self?.loginButtonEnabled.enabled = $0 }
Isolation of side-effects // Pure, functional world let emailChanged: Signal<String,
NoError> let passwordChanged: Signal<String, NoError> let loginButtonEnabled = combineLatest(emailChanged, passwordChanged) .map { !$0.isEmpty && !$1.isEmpty } // Side-effect world self.loginButton.rac.enabled = loginButtonEnabled
Surfacing of co-effects
Surfacing of co-effects ????????????????
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression...
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression... ...then...
Surfacing of co-effects If an effect is a change to
the outside world after executing an expression... ...then... ...a co-effect is the state of the world that the expression needs in order to execute.
Surfacing of co-effects e.g. Dependency Injection
Surfacing of co-effects Dependency Injection func currentUserIsCreator(ofProject project: Project) ->
Bool { return User.currentUser.id == project.creator.id } currentUserIsCreator(ofProject: project) // => true or false
Surfacing of co-effects Dependency Injection func user(_ user: User, isCreatorOfProject:
Project) -> Bool { return user.id == project.creator.id } user(User.currentUser, isCreatorOfProject: project) // => true or false
Surfacing of co-effects References — Colin Barrett — Functional Swift
Conference 2015 — Structure and Interpretation of Swift Programs — The work of Tomas Petricek — Coeffects: A calculus of context-dependent computation — Coeffects: The next big programming challenge
Effect/Co-effect Duality
Code to the interface you wish you had, not the
interface you were given. - Stephen Celis
An interface we were given
An interface we were given Storyboards — Very thick abstraction
layer — Separates code from data — Constantly catching up to what UIKit can do
An interface we wish we had Lenses
An interface we wish we had Lenses struct Project {
let creator: User let id: Int let name: String }
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String>
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String> Project.lens.name .~ "Advanced Swift" // => Project -> Project
An interface we wish we had Lenses Project.lens.name // =>
Lens<Project, String> Project.lens.name .~ "Advanced Swift" // => Project -> Project project |> Project.lens.name .~ "Advanced Swift"
An interface we wish we had Lenses project |> Project.lens.name
.~ "Advanced Swift" |> Project.lens.creator.name .~ "Chris Eidhof"
An interface we wish we had UIKit Lenses
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor>
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor> UIView.lens.backgroundColor .~ .redColor() // => UIView -> UIView
An interface we wish we had UIKit Lenses UIView.lens.backgroundColor //
=> Lens<UIView, UIColor> UIView.lens.backgroundColor .~ .redColor() // => UIView -> UIView view |> UIView.lens.backgroundColor .~ .redColor() |> UIView.lens.layer.cornerRadius .~ 4 |> UIView.lens.layer.masksToBounds .~ true
An interface we wish we had UIKit Lenses func roundedStyle(cornerRadius:
CGFloat) -> (UIView) -> UIView { return UIView.lens.layer.cornerRadius .~ 4 <> UIView.lens.layer.masksToBounds .~ true } view |> roundedStyle(cornerRadius: 4) |> UIView.lens.backgroundColor .~ .redColor()
An interface we wish we had UIKit Lenses let baseButtonStyle
= roundedStyle(cornerRadius: 4) <> UIButton.lens.titleLabel.font .~ UIFont(size: 16) <> UIButton.lens.contentEdgeInsets .~ .init(topBottom: 6, leftRight: 12) let greenButtonStyle = baseButtonStyle <> UIButton.lens.backgroundColor(forState: .Normal) .~ .greenColor()
An interface we wish we had UIKit Lenses let bigButtonStyle
= baseButtonStyle <> UIButton.lens.contentEdgeInsets %~ { .init(top: $0.top * 2, left: $0.left * 2, bottom: $0.bottom * 2, right: $0.right * 2) }
An interface we wish we had UIKit Lenses let baseButtonStyle
= roundedStyle(cornerRadius: 4) <> UIButton.lens.titleLabel.font %~~ { _, button in button.traitCollection.verticalSizeClass == .Compact ? UIFont(size: 12) : UIFont(size: 14) } <> UIButton.lens.contentEdgeInsets .~ .init(topBottom: 6, leftRight: 12)
Principles that we did not benefit so much from: —
D.R.Y. — S.R.P. — S.O.L.I.D. — Objects
The Result
Testing
Test-Driven Development
Test-Driven Bug Fixing
Playground-Driven Development
Screenshot testing
Event Tracking
Event Tracking
Accessibility
Love for UIKit
Be!er working relationship with Product Managers, Designers and Engineers
Finding Happiness in Functional Programming
Finding Happiness in Functional Programming
[email protected]