Den Dribbles

Basics On Programming Paradigms

June 01, 2019

Procedural Program

  • The ideas that programs are a sense of functions
  • Goes from top to bottom
  • Relies heavily on global state, but any line can change the global state
  • C being a procedural language
  • “Imperative” execution
  • Easy to write, difficult to maintain
  • Prone to difficult bugs

Object Oriented

  • Based around a Primitive: object
  • Objects have well defined interfaces
  • Localised behaviour
  • Objects control state
  • Composition
  • Code is still imperative - pro AND con! - Still telling the computer EXACTLY what to do.
  • Can be more verbose

Declarative

  • Describing what you want to happen, but not telling the computer how to do it
  • Eg. SQL, Regex, HTML
  • Data is self-describing
  • As powerful as the interpreter allows
  • As limiting as the interpreter allows - You want build a game in SQL etc.

Functional

  • What we want to happen but not how
  • Little state
  • Few side effects
  • Easy to reason about
  • Composition
  • Expressive
  • Works great with OO
  • Basis in higher math
  • Cons to think differently
  • Not always the best choice
  • No loops, no control logic - Just telling it what we want to happen

Reactive

  • Primitive: Observable
  • Instead of describing data in terms of other data, we describe it in terms of streams of events - From this, we create a pipeline such that we certain data changes, a lot is processed and changed - Example: spreadsheets!
  • Composition
  • Expressive
  • Data flows unidirectionally
  • Tough to think differently
  • Subscriptions help change the data
const cellC2$ = cellA2$.combineLatest(cellB2$).map(cells => cells[0] + cells[1])

cellC2$.subscribe(value => {
  console.log(value)
})

A personal blog on all things of interest. Written by Dennis O'Keeffe, Follow me on Twitter