Functional Programming

(for mortals)

Follow Along

slides.com/willengler/fpmortals/live#/

Tracks

  • Functional Programming for Mortals
  • Ruby on Rails

Tell Us What You Think!

What I'm Gonna Say

  • Why is everyone talking about FP all of a sudden?
  • What is FP?
  • Where can I learn more?

What I Want You to Get Out of It

  • Understand that FP is not just for people with Phd's.
  • Nod thoughtfully when people talk about lambdas.
  • Get amped for the rest of the series.

Part 1: Functional Is Trendy

OOP on Trial

  • "Object Oriented Programming Is an Expensive Disaster which Must End" (link)

Fear

  • Do I need to learn category theory?
  • Do I have to write everything in Clojure now?
  • Does this make me a programming hipster?

Simple Concepts, Big Names

One of those things that I can do that makes me feel competent is to throw around buzzwords and have discussions where it’s like, “Yeah, we all know what we’re talking about here. We’re competent professionals who know what we’re talking about because we know these words. 

- Avdi Grimm

Part 2: Demystifying FP

Functional Programming

... a programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing state and mutable data.

- Wikipedia

Lambda (for Gods)

"... a function definition that is not bound to an identifier.

- Wikipedia

Lambda (for mortals)

"It’s just a chunk of code that you can pass around."

- Charles Max Wood

(code)

What Isn't a Lambda?

If it has a name, it's just a function. (code)

First Class Functions (for Gods)

"... the language supports passing functions as arguments to other functions, returning them as the values from other functions, and assigning them to variables or storing them in data structures."

- Wikipedia

First Class Functions (for mortals)

"You can use functions to build functions."

- Will Engler

(code)

Let's Take a Closer Look

function add_one(func_that_returns_number){
    return function(){
        return func_that_returns_number() + 1
    }
}

This function takes a function as an argument so we call it a higher order function.

When aren't functions first-class?

  • C has function pointers
  • Ability to pass functions around != first-class
void print_secret(){
    printf("Will knows all the words to Shake It Off");
}

void embarrass_will( void (*action)() ){
    /*Implementation classified*/
}

int main(){
    void (*embarrassing_action)();
    embarrassing_action = &print_secret;
    embarrass_will(embarrassing_action);
}

Functional Programming

... a programming paradigm that treats computation as the evaluation of mathematical functions and avoids changing state and mutable data.

- Wikipedia

Part 3: Learn More

Resources I Like

Talks to Come

  • Lambdas and currying in Java 8 (1/26/15)
  • Referential transparency is your friend.
    • On side effects and mutability.
  • Much more! (probably)

Functional Programming for Mortals

By Will Engler

Functional Programming for Mortals

A talk delivered at the 1/12/15 Pitt CSC meeting to kick off the functional programming for mortals track.

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