greister

Advanced 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

Static vs Dynamic dispatch

AKA: Why is consuming an Iterator from glutin so damn hard?

In Rust, like many other languages, there are two different ways to call a function: static and dynamic dispatch. They're used in different scenarios and each have their own pros and cons, which are summarised thusly:

Static calls tend to be faster because they do not require the use of a lookup table, which incurs overhead as the compiler has to 'find' the function it is calling at runtime.
Dynamic calls tend to be more conservative of space as they can be re-used. This isn't so much an issue with functions like strcpy, but with functions that have multiple types of arguments (generics, for example), the code for the function must be duplicated.

	# Author: Miodrag Milic <[email protected]>
	# Last Change: 12-Feb-2016.

	param(
	# Path to Excel file
	[string] $Path
	)

	if (!(Test-Path $Path)) { throw Path not found: $Path }
	ps excel -ea 0\| kill

	# 并发查询所有上游DNS服务器
	all-servers
	# 本地DNS缓存最小有效期
	min-cache-ttl=3600
	# 本地DNS缓存数目
	cache-size=65535
	# 上游DNS服务器, 可设置多个
	server=8.8.4.4
	#server=8.8.8.8
	server=114.114.114.114

	def f(num:Int,arr:List[Int]):List[Int] = {
	if (!arr.isEmpty)
	for ( i <- 1 to num) println(arr.head)
	f(num, arr.tail)

	}

	sudo apt-get remove scala-library scala
	sudo wget www.scala-lang.org/files/archive/scala-2.10.4.deb
	sudo dpkg -i scala-2.10.4.deb
	sudo apt-get update
	sudo apt-get install scala
	wget http://scalasbt.artifactoryonline.com/scalasbt/sbt-native-packages/org/scala-sbt/sbt/0.12.4/sbt.deb
	sudo dpkg -i sbt.deb
	sudo apt-get update
	sudo apt-get install sbt

	import scala.xml._

	// To convert a Maven pom.xml to build.sbt:
	// 1) Place this code into a file called PomToSbt.scala next to pom.xml
	// 2) Type scala PomtoSbt.scala > build.sbt
	// The dependencies from pom.xml will be extracted and place into a complete build.sbt file
	// Because most pom.xml files only refernence non-Scala dependencies, I did not use %%
	val lines = (XML.load("pom.xml") \\ "dependencies") \ "dependency" map { dependency =>
	val groupId = (dependency \ "groupId").text
	val artifactId = (dependency \ "artifactId").text

	(defun re-seq (regexp string)
	"Get a list of all regexp matches in a string"
	(save-match-data
	(let ((pos 0)
	matches)
	(while (string-match regexp string pos)
	(p


	(car (replace-regexp-in-string "\\n" "" (shell-command-to-string
	"node -e 'console.log(module.paths)'")))

	--------------------------------------
	error:

	Debugger entered--Lisp error: (wrong-type-argument listp

	;;; Try to find the string at point as a NodeJS module

	(require 'ffap)

	(defun ffap-nodejs-module (name)
	(unless (or (string-prefix-p "/" name)
	(string-prefix-p "./" name)
	(string-prefix-p "../" name))
	(let ((base (locate-dominating-file
	default-directory