Tutorial by Examples: composition

Composition provides an alternative to inheritance. A struct may include another type by name in its declaration: type Request struct { Resource string } type AuthenticatedRequest struct { Request Username, Password string } In the example above, AuthenticatedRequest will con...

A Swift String is made of Unicode code points. It can be decomposed and encoded in several different ways. let str = "ที่👌①!" Decomposing Strings A string's characters are Unicode extended grapheme clusters: Array(str.characters) // ["ที่", "👌", "①", ...

Partial functions are often used to define a total function in parts: sealed trait SuperType case object A extends SuperType case object B extends SuperType case object C extends SuperType val pfA: PartialFunction[SuperType, Int] = { case A => 5 } val pfB: PartialFunction[SuperType,...

'Prefer composition over inheritance' is an important and popular programming principle, used to assign behaviors to objects, as opposed to inheriting many often unneeded behaviors. Behaviour factories var speaker = function (state) { var noise = state.noise || 'grunt'; return { ...

Class composition allows explicit relations between objects. In this example, people live in cities that belong to countries. Composition allows people to access the number of all people living in their country: class Country(object): def __init__(self): self.cities=[] ...

Any array can be quickly decomposed by assigning its elements into multiple variables. A simple example: arr = [1, 2, 3] # --- a = arr[0] b = arr[1] c = arr[2] # --- or, the same a, b, c = arr Preceding a variable with the splat operator (*) puts into it an array of all the elements that h...

Hibernate has some strategies of inheritance. The JOINED inheritance type do a JOIN between the child entity and parent entity. The problem with this approach is that Hibernate always bring the data of all involved tables in the inheritance. Per example, if you have the entities Bicycle and Mounta...

(.) lets us compose two functions, feeding output of one as an input to the other: (f . g) x = f (g x) For example, if we want to square the successor of an input number, we can write ((^2) . succ) 1 -- 4 There is also (<<<) which is an alias to (.). So, (+ 1) <<&lt...

Control.Category defines (>>>), which, when specialized to functions, is -- (>>>) :: Category cat => cat a b -> cat b c -> cat a c -- (>>>) :: (->) a b -> (->) b c -> (->) a c -- (>>>) :: (a -> b) -> (b -> c) -> (a -> c...

The regular composition works for unary functions. In the case of binary, we can define (f .: g) x y = f (g x y) -- which is also = f ((g x) y) = (f . g x) y -- by definition of (.) = (f .) (g x) y = ((f .) . g) x y Thus,...

Function composition allows for two functions to operate and be viewed as a single function. Expressed in mathematical terms, given a function f(x) and a function g(x), the function h(x) = f(g(x)). When a function is compiled, it is compiled to a type related to Function1. Scala provides two method...

Intent: Separate the construction of a complex object from its representation so that the same construction process can create different representations Builder pattern is useful when you have few mandatory attributes and many optional attributes to construct a object. To create an object with dif...

Arrow is, vaguely speaking, the class of morphisms that compose like functions, with both serial composition and “parallel composition”. While it is most interesting as a generalisation of functions, the Arrow (->) instance itself is already quite useful. For instance, the following function: sp...

The "child" components of a component are available on a special prop, props.children. This prop is very useful for "Compositing" components together, and can make JSX markup more intuitive or reflective of the intended final structure of the DOM: var SomeComponent = function ...

You can use Modules to build more complex classes through composition. The include ModuleName directive incorporates a module's methods into a class. module Foo def foo_method puts 'foo_method called!' end end module Bar def bar_method puts 'bar_method called!' end end ...

Ruby moves up on ancestors chain of an object. This chain can contain both modules and classes. Same rules about moving up the chain apply to modules as well. class Example end module Prepended def initialize *args return super :default if args.empty? super end end module Fi...

Composing multiple functions into one is a functional programming common practice; composition makes a pipeline through which our data will transit and get modified simply working on the function-composition (just like snapping pieces of a track together)... you start out with some single responsi...

We can define a function to perform function composition using anonymous function syntax: f ∘ g = x -> f(g(x)) Note that this definition is equivalent to each of the following definitions: ∘(f, g) = x -> f(g(x)) or function ∘(f, g) x -> f(g(x)) end recalling that in Julia,...

The Cholesky decomposition is a method to decompose an hermitean, positiv definite matrix into an upper triangular matrix and its transpose. It can be used to solve linear equations systems and and is around twice as fast as LU-decomposition. A = [4 12 -16 12 37 -43 -16 -43 98]; R = chol...

This method will decompose a matrix into an upper triangular and an orthogonal matrix. A = [4 12 -16 12 37 -43 -16 -43 98]; R = qr(A); This will return the upper triangular matrix while the following will return both matrices. [Q,R] = qr(A); The following plot will display the run...