Tianhao tianhao-au

Collections Redesign Proposal

I'm going to start off by motivating what I'm doing here. And I want to be clear that I'm not "dissing" the existing collections implementation or anything as unproductively negative as that. It was a really good experiment, it was a huge step forward given what we knew back in 2.8, but now it's time to learn from that experiment and do better. This proposal uses what I believe are the lessons we can learn about what worked, what didn't work, and what is and isn't important about collections in Scala.

This is going to start out sounding really negative and pervasively dismissive, but bear with me! There's a point to all my ranting. I want to be really clear about my motivations for the proposal being the way that it is.

Problems

Generic Interfaces

Applied Functional Programming with Scala - Notes

1. Mastering Functions

A function is a mapping from one set, called a domain, to another set, called the codomain. A function associates every element in the domain with exactly one element in the codomain. In Scala, both domain and codomain are types.

val square : Int => Int = x => x * x

Most of what's written in this article is deliberately biased and wrong. It is yet another in the stream of Scala-hating posts that people. I analyze the article below:

TIOBE index is a metric based on search engine ranking policies and can be intentionally or unintentionally gamed.

https://blog.timbunce.org/2009/05/17/tiobe-index-is-being-gamed/

On these rankings, Scala is quite high:

Getting Started in Scala

This is my attempt to give Scala newcomers a quick-and-easy rundown to the prerequisite steps they need to a) try Scala, and b) get a standard project up and running on their machine. I'm not going to talk about the language at all; there are plenty of better resources a google search away. This is just focused on the prerequisite tooling and machine setup. I will not be assuming you have any background in JVM languages. So if you're coming from Python, Ruby, JavaScript, Haskell, or anywhere… I hope to present the information you need without assuming anything.

Disclaimer It has been over a decade since I was new to Scala, and when I was new to Scala, I was coming from a Java and Ruby background. This has probably caused me to unknowingly make some assumptions. Please feel free to call me out in comments/tweets!

One assumption I'm knowingly making is that you're on a Unix-like platform. Sorry, Windows users.

	object TypeclasseDemo {

	// The parts of the type class pattern are:
	//
	// 1. the "type class" itself -- a trait with a single type parameter;
	//
	// 2. type class "instances" for each type we care about,
	// each marked with the `implicit` keyword;
	//
	// 3. an "interface" to the type class -- one or more methods

	package org.snippets

	import scala.collection.immutable.Stream.#::
	import scala.util.{Failure, Success, Try}

	class InsufficientParametersException(message: String) extends RuntimeException(message)

	object Tailrec2Fold {
	type RpnModel = String
	type CalculationState = (String, String)