#higher-order functions

[mdhighfi-blog]

W6D1 - Asteroids

Flying Circles

Remember that game where you fly around in a spaceship shooting asteroids and try not to get hit? We started that today! Right now it isn't much more than some circles (asteroids) moving around on a screen. Still, the canvas is pretty powerful and fun to work with, and I'm looking forward to finishing this project.

Currying

Haskell Curry was a 20th century mathematician who worked in logic. The functional programming language Haskell is named after him. So is one of the operations you can do in Haskell: currying. Today as a warmup exercise for Asteroids we wrote our own currying higher-order function in JavaScript. It sounds fancy, but all it really means is that you can create a new function out of an old one by holding one of its arguments constant. For example. if f(x, y, z) = x + y + z, then currying f, you could get a function g(y, z) = 5 + y + z, which is just f where x = 5. Using recursion and callbacks in JavaScript to do this was fun and enlightening.

[terenceng]

higher order functions MEANS a function that take another function as an input parameter. Which should be quite useful when we need to create some general functions that is essential to different classes.

example with underscorejs:

var msg = _.template("hello <%=planet %>");

var planets = ["sun","earth","mars"];

_.each(planets,yell);

function yell (something){  var what = msg({planet:something});  console.log(what); }

http://jsbin.com/yuwozopovo/1/edit?html,js,console,output

http://underscorejs.org/#each

[szabolcs-learns-scala]

One of my colleague recommended it. I'm trying to rewrite these explanations because of I really don't know the Higher-order functions. How these works. I don't have image in my mind about these functions, yet.

[isomorphismes]

You can't pay people enough to carefully debug boring boilerplate code. I've tried.

Yaron Minsky

[fuckyeahterminals]

Breaking Down Conditional Statments to Something Cool

So I KNOW that as a programmer YOU have run into this issue when testing a condition

var a = 10; if (a <= 100 && a > -3 && a != 5) { do something; }

Yeah, uh, Fuck this, why cant I just list the conditions and check it against it instead of having to write 'a' and '&&' every single fucking time.

This is how I deal with validation in Haskell

list = [ (> 2), (< 100), (/= 5) ] condition = and $ map (\c -> c a) list if condition then do something else do something

AND I know there's skeptics out there saying well what if you need to 'and' some stuff and 'or' other stuff. You're working with lists, you can manipulate to do what I did with the base list in the first place and do a higher-order again.

Also you can inline the condition, it's way easier to read, you can prioritize your conditions and your code can be a bit more encapsulated, maybe you only need a parameter to meet the first x-amount of conditions so you could do something like

lessStrenousCondition = or $ map (\c -> c a) list $ take 2 list

Idk I've been doing validation code at work in C# and I have to write some pretty verbose statements, it's annoying (knowing the fucking language I can import some library to get something similar, but i mean this is part of the Language for Haskell).

edit*

Also if you're wondering why this work is because [(function literal)] is actually of type [Integer -> Bool] what that means it that it's an array of objects which take an integer and return a Boolean statement.

So in Haskell

(> 10) 5

is a legal statement that checks if 5 meets the condition "is it greater than 10"

[tomleos]

This tool lets you visualize how the python interpreter executes python code. I haven't seen a better visualization of how a snippet of code is being executed since coding in the Racket IDE.