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![PURE FUNCTIONS
DECLARATIVE PROGRAMMING
REFERENTIAL TRANSPARENCY
INMUTABILITY
// Imperative programming
var arrayFoo = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9];
for (var i = 0; i < arrayFoo.length; i++) {
arrayFoo[i] = Math.pow(arrayFoo[i], 2);
}
array; // [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
// Declarative programming
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9].map(num => Math.pow(num, 2));
// [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]](https://image.slidesharecdn.com/frp-170321120412/75/Functional-Reactive-Programming-10-2048.jpg)
Uploaded byFelipe Hernández Rivas
Functional Reactive Programming
This document discusses functional reactive programming and reactive programming concepts. It compares imperative programming to declarative and reactive programming. Functional programming uses pure functions to create immutable programs without side effects. Reactive programming involves asynchronous data streams that are sequences of ongoing events ordered over time. The document provides code examples demonstrating pure vs impure functions, referential transparency, and reactive programming with RxSwift.
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- 5. // Imperative programming varx = 1, y = 2, z = y + x; console.log(z); //3 x = 2; console.log(z); //3 // Reactive programming var x = 1, y = 2, z = y + x; console.log(z); //3 x = 2; console.log(z); //4
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- 9. FUNCTIONAL PROGRAMMING DECLARATIVE EVALUATIONOF PURE FUNCTIONS TO CREATE IMMUTABLE PROGRAMS AND SO AVOID SIDE EFFECTS THAT ARE EXTERNALLY OBSERVED.
- 10. PURE FUNCTIONS DECLARATIVE PROGRAMMING REFERENTIALTRANSPARENCY INMUTABILITY // Imperative programming var arrayFoo = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]; for (var i = 0; i < arrayFoo.length; i++) { arrayFoo[i] = Math.pow(arrayFoo[i], 2); } array; // [0, 1, 4, 9, 16, 25, 36, 49, 64, 81] // Declarative programming [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].map(num => Math.pow(num, 2)); // [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
- 11. PURE FUNCTIONS DECLARATIVE PROGRAMMING REFERENTIALTRANSPARENCY INMUTABILITY // Impure function var likes = 0; function addLike() { return ++likes; } // Pure function function addLike(likes) { return ++likes; } addLike(addLike(0)); // 2
- 12. DECLARATIVE PROGRAMMING REFERENTIAL TRANSPARENCY INMUTABILITY PUREFUNCTIONS // Referential transparent function int plusOne(int x) { return x+1; } // Referential opaqueness function int G = 10; int plusG(int x) {//G can be modified externally returning different values. return x + G; }
- 13. DECLARATIVE PROGRAMMING REFERENTIAL TRANSPARENCY INMUTABILITY PUREFUNCTIONS // Referential transparent function int plusOne(int x) { return x+1; } // Referential opaqueness function int G = 10; int plusG(int x) {//G can be modified externally returning different values. return x + G; }
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- 15. : https://goo.gl/NaMmJ : https://goo.gl/sGSwMS Reactiveprogramming is programming with asynchronous data streams.
- 16. A stream isa sequence of ongoing events ordered in time.
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- 20. // RxSwift LoginViewModel structLoginViewModel { let usernameBGColor: Driver<UIColor> let passwordBGColor: Driver<UIColor> let credentialsValid: Driver<Bool> init(usernameText: Driver<String>, passwordText: Driver<String>) { let usernameValid = usernameText .distinctUntilChanged() .throttle(0.3) .map { $0.utf8.count > 3 } let passwordValid = passwordText .distinctUntilChanged() .throttle(0.3) .map { $0.utf8.count > 3 } usernameBGColor = usernameValid .map { $0 ? BG_COLOR : UIColor.white } passwordBGColor = passwordValid .map { $0 ? BG_COLOR : UIColor.white } credentialsValid = Driver.combineLatest(usernameValid, passwordValid) { $0 && $1 } } func login(_ username: String, password: String) -> Observable<AutenticationStatus> { return AuthManager.sharedManager.login(username, password: password) }