Joe Karlsson
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Functional Programming
For People That Hate Math
slides.com/joekarlsson | @joekarlsson1
I am
Joe Karlsson
Software Engineer
How's this going to work?
What have y'all heard about FP?
Functional Programming
is unfamiliar territory for most
If you want everything to be familiar you will never learn anything new.
- Rich Hickey (Author of Clojure)
Programming Paradigms
Imperative
HOW it should run
Or like giving instructions to an idiot
const arr = [1, 2, 3, 4, 5];
const doubler = (arr) => {
for (let i=0; i<arr.length; i++) {
arr[i] = arr[i] * 2;
}
return arr;
};
const doubleArr = doubler(arr);
console.log(doubleArr); // [2, 4, 6, 8, 10]Object Oriented
class Foo {
constructor(arr) {
this._arr = arr;
}
getSum() {
let sum = 0;
for (let i=0; i<this._arr.length; i++) {
sum += this._arr[i];
}
return sum;
}
}
const arr = [1, 2, 3, 4, 5];
const foo = new Foo(arr);
transformer.getSum(); // 15Declarative
WHAT should happen
SELECT EmployeeID, FirstName, LastName
FROM Employees
WHERE City = 'London'INSERT INTO student (id, name, age)
VALUES (‘1’, ‘alan’, 28);DELETE FROM student
WHERE name = ‘alan’;Functional
*WHAT should happen
Is a list of things you CAN'T do
- No Assignments
- No Side Effects
- No Mutating or changing state
- No While/For Loops
What CAN I do?
Functional Programming is so called because a program consists entirely of functions.
- John Hughes , Why Functional Programming Matters
Why?
No matter what language you work in, programming in a functional style provides benefits. You should do it whenever it is convenient, and you should think hard about the decision when it isn't convenient.
- John Carmack, ID Software
-
More concise
-
More performant
-
Easy to reason*
-
Easy to debug
-
Co-exists very well with code written in other styles
-
Gives you more ways to solve problems.
No Side Effects
Doesn’t rely on data outside the current function
Doesn’t change data that exists outside the current function
// unfunctional function:
a = 0
const increment = () => {
return ++a;
};
increment();
increment();
increment();// unfunctional function:
a = 0
const increment = () => {
return ++a;
};
increment(); // 1
increment(); // 2
increment(); // 3// functional function:
const num = 0;
const increment = (a) => {
return a + 1;
};
increment(num);
increment(num);
increment(num);// functional function:
const num = 0;
const increment = (a) => {
return a + 1;
};
increment(num); // 1
increment(num); // 1
increment(num); // 1No For/While Loops
Map
Takes a collection of items and returns a new collection of items that have been changed
const arr = [1, 2, 3, 4, 5];
const doubler = (element) => {
return element * 2;
};
const doubleArr = arr.map(doubler);
console.log(doubleArr); // [2, 4, 6, 8, 10]Reduce
Takes a collection of items. It returns a value that is created by combining the items.
const arr = [1, 2, 3, 4, 5];
const summarizer = (previous, current) => {
return previous + current;
};
const sum = arr.reduce(summarizer);
console.log(sum); // 15Docs: Reduce [MDN]
Demo
-
FP describes WHAT should happen
-
No Assignments
-
No Varying Your Variables. (Immutable)
-
No While/For Loops
-
No Side Effects
-
No Mutating or changing state
How do you get better?
Additional Resources
-
Elm (pure FP language purpose-built for front-end web development)
http://elm-lang.org/
Joe Karlsson
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Functional Programming For People That Hate Math
By Joe Karlsson
Functional Programming For People That Hate Math
Many of us have heard of Functional Programming, and all the benefits it is supposed to bring to our code. You may have also heard that it's really hard and kinda "mathy." You will learn how can it be applied to the real-world without have a Master degree in Mathematics.
