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FUNCTIONAL PROGRAMMING IN A NUTSHELL
Adityo Pratomo (Framework)TiA PDC’17
HELLO, I’M DIDIT
Chief Academic OfficerFroyo Framework
Jakarta-based IT trainer provider
CTO & Production ManagerLabtek Indie
Bandung-based Digital Product R&D Company
HELLO, I’M DIDIT
I mainly developInteractive graphics,
game, hardware
OVERVIEW
What is functional programming?
Functional programming vs imperative programming
Building block of functional programming
How functional programming will help you?
PROGRAMMING
programmer source code computer
Co-workers
Thoughts into codes
Codes into instructions
Read code for analysis
Programmers are required to instruct machine and communicate to humans
WHILE solving problems according to set of rules (languages, frameworks, hardware architecture, and so forth)
TOOLS FOR PROGRAMMERS
Software
Frameworks
Programming Language
Programming Paradigm
Functional Programming
Functional programming is a programming paradigm—a style of building the structure and elements of computer programs—that treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data.
It is a declarative programming paradigm, which means programming is done with expressions or declarations instead of statements.
treats computation as the evaluation of mathematical functions and avoids changing-state and mutable data
FUNCTIONAL VS IMPERATIVE: AN ANALOGY
MI REBUS: THE IMPERATIVE WAY
1. Pour water into saucepan
2. Turn on stove to boil the water
3. After the water boils, insert the noodle
4. Add seasonings
5. Cook for 3 minutes
6. Pour noodle from the saucepan along with the soup to a bowl
MI REBUS: THE FUNCTIONAL WAY
1. Mi rebus components:i. Boiling waterii. Cooked noodle and seasoningsiii. Served noodle on bowl
2. Compositions of components:i. Serve(cooked(boiled(noodle and seasonings)))
FUNCTIONAL VS IMPERATIVE
1. Pour water into saucepan
2. Turn on stove to boil the water
3. After the water boils, insert the noodle
4. Add seasonings
5. Cook for 3 minutes
6. Pour noodle from the saucepan along with the soup to a bowl
1. Mi rebus components:i. Boiling waterii. Cooked noodle and seasoningsiii. Served noodle on bowl
2. Compositions of components:i. Serve(cooked(boiled(noodle and
seasonings)))
Imperative:1. Focuses on HOW to do things2. A set of sequential instructions3. Depends on state to operate4. Not necessarily reusable, each new
product might require using set of new instructions
Functional:1. Focuses on WHAT is a thing2. Composing set of functions, each
functions has a clear result3. Not depends on state4. Each functions can be reused by
including in different compositions
FUNCTIONAL VS IMPERATIVE
Menghitung nilai terbesar dan rata-rata dari sebuah data
FUNCTIONAL VS IMPERATIVE
Menghitung nilai terbesar dan rata-rata dari sebuah data
FUNCTIONAL VS IMPERATIVE
• Functions are being used to describe a step-by step instructions of doing things
• Relies on for loop• Involves temporary mutable variable to store
state
• Functions are being used to describe a desired result from an operation
• Relies on array method• No mutable variable and no state
FUNCTIONAL VS IMPERATIVE
Normalize the numbers by:
- Count average
- Increase numbers smaller than average
- Decrease numbers smaller by average
BUILDING BLOCKS OF FUNCTIONAL PROGRAMMING1. Immutable data A data whose value(s) can’t be change
2. Pure function A function whose return value is only
determined by its input values, without observable side effects
Produce the same output when processing the same input
const myData = [51, 72, 38, 94];
function isEven (x) {if (x % 2 == 0) {
return true;}
}
PURE FUNCTIONS AND FUNCTION COMPOSITION
Always returns a function or value
A reusable building block of a program
Several functions can be composed to do data processing, creating a new function
f(x) => y
g(x) => z
f o g (x) = f(g(x))
function compose (f, g) {return function (x) {
return f(g(x));}
}
function add2(x) {return x + 2;
}
function multiply4(x) {return x*4;
}
var add2Multiply4 = compose(add2, multiply4);console.log(add2Multiply4(2));
PURE FUNCTIONS AND FUNCTION COMPOSITION
const albumList = [{
artist: "Metallica",title: "Master of Puppets",year: 1986
},{
artist: "Metallica",title: "Black Album",year: 1990
},{
artist: "Megadeth",title: "Rust in Peace",year: 1990
}]
const getMetallica = (arr) => arr.filter((item) => item.artist === 'Metallica');
const getAlbumIn1990 = (arr) => arr.filter((item) => item.year === 1990);
const getMetallicaAlbumIn1990 = compose(getMetallica, getAlbumIn1990);
console.log(getMetallicaAlbumIn1990(albumList));
//[ { artist: "Metallica", title: "Black Album", year: 1990 }],
HOW FUNCTIONAL PROGRAMMING HELPS?
Pure functions
Immutable Data
Create testable software from the ground up
Reduce bugs Create multithread application
Create true modular software
WHERE CAN I USE IT?
-Back end:- Various data processing and simulation (Scala, Haskell, Clojure, Elixir, Erlang, etc.)
-Front end:- One way data rendering (Elm)
-Anywhere:- Code in your favourite language using functional programming style (C#, C++, JavaScript, Python)
LAST NOTE
Pure functional programming have no side effects Real world application relies on side effects for I/O operation Use functional style to manage the side effects
Functional programming doesn’t use state Game programing relies on state to manage the game (level, progressions, health, etc) Use state to manage, but inner operations can still use FP
