Functional Programming& Immutable Data

Functional programmingFunctional programming is a programming paradigm

that treats computation as the evaluation of mathematical functions and avoids changing-state

and mutable data.

Functional programmingIs the programming using mathematical functions

Mathematical functionsThe representations of expressions that when called

will return ever the same result.

I = V/R

current(voltage,resistance) = voltage/resistance;

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

current(1,1000) = 1/1000; is equal 0.001

No matter how many times you apply!

Ever result will be equal!

Contrast

Imperative

This is about "how"!

Functional

This is about “what”!

High-order functions

Lazy valuation

High-order functions Is a function that takes one or more functions as arguments and

can returns a function as its result.

Lisp, Erlang, Haskell, Javascript, Java8, Scala…

List, HashMap, Map, Reduce, Filter, Reject, ForEach

List, HashMap

ReduceIterate over the list and reduce the list values in one value.

MapIterate over a list and create other list with results of operations applied each item of list.

High-order functions Is a function that takes one or more functions as arguments and

can returns a function as its result.

Then! Functional programming is a style of programming that compose functions to produce

one result.

This is a new mindset.

Because in this scene, the minor part of your architecture is not more a "Classe", now is a "Function".

Now you need creating pieces for transform inputted data with focus on the desired result.

Example

I have a list of people and I need all people who have more than 18 years old.

Count how many times a letter repeats but only on the people who have more than 18 years old.

When your code is divided in very small pieces is easy for you code using single

responsibility.

You reuse more and write less.

Debugging is simple

The TDD and BDD is pretty simple

You win a powerful approach for improve performance

MemoizationIn computing, memoization is an optimization

technique used primarily to speed up computer programs by storing the results of expensive function

calls and returning the cached result

numbers.map(sum)

P1

P2

P3

P4

Cluster

Big Data

Realtime applications

Immutable dataThe value is not changed in life cycle, like constants.

The data is created to receive changes, like variables.

Mutable data

The biggest problems with mutable data is that you need worry with scopes, concurrency and parallelism.

Mutable data

Immutable data is only a good idea! But in functional programing its is the main ideia.

You couldn't change the asks, only create answers.

This is more fluid, because the flows is very predictable.

My motivation for this talk is about

REDUX

Only one entry point immutable. Single state.

Apply reducers for produce new state.

Simplify tests, write less and improve productivity.

SimplesDental

Luiz H. Estácioluizstacio

luiz@simplesdental.com😎

Thanks 😁