composition

问题 I understand mixin as what looks like inheritance but what is more like composition. (edit: I tend to think giving additional functionality/attributes by mixin rather than giving another is-a relationship .) Mentally, I'm saying something like this when I use mixin: I'm giving you this mixin you are missing, rather than you are actually this mixin-type as well.(is-a) And I read few times, you should prefer composition over inheritance. We could just use straight compositions instead of mixins

问题 I understand mixin as what looks like inheritance but what is more like composition. (edit: I tend to think giving additional functionality/attributes by mixin rather than giving another is-a relationship .) Mentally, I'm saying something like this when I use mixin: I'm giving you this mixin you are missing, rather than you are actually this mixin-type as well.(is-a) And I read few times, you should prefer composition over inheritance. We could just use straight compositions instead of mixins

问题 I wrote a function "rep" that takes a function f and takes n compositions of f. So rep(square,3) behaves like this: square(square(square(x))). And when I pass 3 into it, rep(square,3)(3)=6561. There is no problem with my code, but I was wondering if there was a way to make it "prettier" (or shorter) without having to call another function or import anything. Thanks! def compose1(f, g): """Return a function h, such that h(x) = f(g(x)).""" def h(x): return f(g(x)) return h def rep(f,n): newfunc

问题 I wrote a function "rep" that takes a function f and takes n compositions of f. So rep(square,3) behaves like this: square(square(square(x))). And when I pass 3 into it, rep(square,3)(3)=6561. There is no problem with my code, but I was wondering if there was a way to make it "prettier" (or shorter) without having to call another function or import anything. Thanks! def compose1(f, g): """Return a function h, such that h(x) = f(g(x)).""" def h(x): return f(g(x)) return h def rep(f,n): newfunc

问题 I wrote a function "rep" that takes a function f and takes n compositions of f. So rep(square,3) behaves like this: square(square(square(x))). And when I pass 3 into it, rep(square,3)(3)=6561. There is no problem with my code, but I was wondering if there was a way to make it "prettier" (or shorter) without having to call another function or import anything. Thanks! def compose1(f, g): """Return a function h, such that h(x) = f(g(x)).""" def h(x): return f(g(x)) return h def rep(f,n): newfunc

问题 Based on this awesome Composition over Inheritance video by MPJ, I've been trying to formulate composition in TypeScript. I want to compose classes , not objects or factory functions. Here is my effort so far (with a little help from lodash ): class Barker { constructor(private state) {} bark() { console.log(`Woof, I am ${this.state.name}`); } } class Driver { constructor(private state) {} drive() { this.state.position = this.state.position + this.state.speed; } } class Killer { constructor

问题 I have several pairs of structs for which the fields of one is a perfect superset of the other. I'd like to simulate some kind of inheritance so I don't have to have separate cases for each struct since that would almost double my code. In a language like C, I could simulate inheritance of fields with something like this: struct A { int a; }; struct B { struct A parent; int b; }; main() { struct B test1; struct A *test2 = &test1; test2->a = 7; } I want to do something like this in Rust. I

问题 This question already has an answer here : What is the monomorphism restriction? (1 answer) Closed last month . I have the following file: module SimpleComposition where class Domain a where f :: a -> a g :: a -> a h = f . g When trying to loading it in ghci, I get the error src\play.hs:7:5: error: * No instance for (Domain c0) arising from a use of `f' * In the first argument of `(.)', namely `f' In the expression: f . g In an equation for `h': h = f . g I believe the problem is that the

问题 This question already has an answer here : What is the monomorphism restriction? (1 answer) Closed last month . I have the following file: module SimpleComposition where class Domain a where f :: a -> a g :: a -> a h = f . g When trying to loading it in ghci, I get the error src\play.hs:7:5: error: * No instance for (Domain c0) arising from a use of `f' * In the first argument of `(.)', namely `f' In the expression: f . g In an equation for `h': h = f . g I believe the problem is that the

问题 I see occational references to delegation, or the delegation design pattern in Julia. What is this? E.g. I see it mentioned in This file in DataStructures.jl 回答1: This is a form of polymorphism via composition (rather than inheritance) Say one has a wrapper type, wrapping some instance of a concrete subtype of AbstractT where the wrapper itself is intended to be a subtype of AbstractT (Not nesc always true, but in general). To add all the methods one exacts such a subtype of AbstractT to have