Roberto Bonvallet rbonvall

Things that programmers don't know but should

(A book that I might eventually write!)

Gary Bernhardt

I imagine each of these chapters being about 2,000 words, making the whole book about the size of a small novel. For comparison, articles in large papers like the New York Times average about 1,200 words. Each topic gets whatever level of detail I can fit into that space. For simple topics, that's a lot of space: I can probably walk through a very basic, but working, implementation of the IP protocol.

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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

Purity and pure FP

purity is a syntactical property of programs, more precisely defined as referential transparency: replacing an expression for its bound value doesn't change meaning (precise definition)
side effects are things that break referential transparency (precise definition)
There's no direct connection between the concepts of IO, State and so on, and side effects. Traditionally, these things are side effectful (break referential transparency), but you can have abstractions that are pure (don't break ref.trans.)
Due to the above, the term purely functional programming is not an oxymoron, it makes perfect sense.
In haskell style pure FP, type constructors and algebras are used to represent "things that would otherwise traditionally be side effects (break ref.trans.)". We call these F[_]s effects or computational contexts for brevity. You can see for yourself how this cannot be a precise definition (especially because they could also have kind higher than * -> *, even though most famous a

David's programming examples knowledge base

Generated by code-examples-manager release 2.4.9-SNAPSHOT
659 published examples

akka-pekko

akka-actors-hello-world.sc : Simple akka hello world example
akka-capitalize-and-print.sc : dump capitalized string coming from stdin using streams
akka-http-client-json-stream.sc : Fully asynchronous http client call with json streamed response using akka-http will work in all cases, even with chunked responses !
akka-http-client-json-with-proxy.sc : Fully asynchronous http client call with json response using akka-http will work in all cases, even with chunked responses, this example add automatic http proxy support.
[akka-http-client-json.sc](https:/

Invertible syntax descriptions

An "invertible syntax description" is something that can be used to both parse and generate a syntax. For example, instead of defining separate toJson and fromJson functions for a given data type, an invertible syntax description could be used to provide both. There are many Haskell libraries that provide this functionality or something close to it. As far as I can tell most of them are at least inspired by Invertible syntax descriptions by Tillmann Rendel and Klaus Ostermann.

Personally I am interested in using these for HTTP routing. I frequently want to be able to define a route such as /episodes/:id.json, dispatch based on that route, and generate links to that route. Doing so manually is tedious and error prone.

	object InstantInsanity extends App {

	// scalastyle:off

	def undefined[T]: T = ???
	def ⊥[T]: T = undefined

	trait R
	trait G
	trait B

	$ curl --help
	Usage: curl [options...] <url>
	--abstract-unix-socket <path> Connect via abstract Unix domain socket
	--alt-svc <file name> Enable alt-svc with this cache file
	--anyauth Pick any authentication method
	-a, --append Append to target file when uploading
	--basic Use HTTP Basic Authentication
	--cacert <file> CA certificate to verify peer against
	--capath <dir> CA directory to verify peer against
	-E, --cert <certificate[:password]> Client certificate file and password

	#/bin/sh

	speed="0.7"

	mkdir "speed-${speed}x"

	for f in *.mp3
	do ffmpeg -i "$f" -filter:a "atempo=${speed}" "./speed-${speed}x/$f"
	done

	#!/usr/bin/awk -f

	# This program is a copy of guff, a plot device. https://github.com/silentbicycle/guff
	# My copy here is written in awk instead of C, has no compelling benefit.
	# Public domain. @thingskatedid

	# Run as awk -v x=xyz ... or env variables for stuff?
	# Assumptions: the data is evenly spaced along the x-axis

	# TODO: moving average