TeaDrivenDev

Paying It F#rward

This article is an entry in the 2019 F# Advent Calendar in English. Thanks to Sergey Tihon for organizing it, as always!

Note: This belongs on my blog, but some things are broken there right now, probably due to changes to GitHub Pages in recent years, so I'm publishing this here for now to at least get a reliable output.

The F# community, while small compared to those of many other languages, is known to be exceedingly open and helpful to beginners. I experienced this myself when I started learning the language nearly six years ago, and people (especially the F# MVPs) were always quick and eager to answer my newbie questions on Twitter, or wrote extensive answers on Stack Overflow or Code Review. Havi

keathley

defmodule Demo do
  def demo do
    _once_per_second = Demo.start(:once, 200)
    _ten_per_second = Demo.start(:ten, 220)
    _hundret_per_second = Demo.start(:hundret, 250)

    IO.puts("Launced processes")
    Process.sleep(1_500)
    [:once, :ten, :hundret] |> show() |> IO.inspect()

nilaydshah

import argparse
import sys 
import grp
import pwd
import subprocess
import os
import json

class PreRegistration:

rrrene

defmodule Converter do
  def convert_image(_a, _b, _c) do
    :ok
  end
end

defmodule Converter.StepBuilder do
  defmacro __using__(_opts \\ []) do
    quote do
      Module.register_attribute(__MODULE__, :steps, accumulate: true)

IcyApril

#!/bin/bash

echo -n Password:
read -s password
echo
hash="$(echo -n $password | openssl sha1)"
upperCase="$(echo $hash | tr '[a-z]' '[A-Z]')"
prefix="${upperCase:0:5}"
response=$(curl -s https://api.pwnedpasswords.com/range/$prefix)
while read -r line; do

KronicDeth

Elixir Native UI - Boyd Multerer https://www.youtube.com/watch?v=77FW-jrCyCs

• Only dependencies are Elixir, Erlang, and glut to access OpenGL.
• No UI threads! Individual processes can be used to track mouse
• Slides track mouse as long as button is down https://youtu.be/77FW-jrCyCs?t=37m35s
• Sliders can be rotated https://youtu.be/77FW-jrCyCs?t=40m4s
• 500 lines animating still a few ms to render https://youtu.be/77FW-jrCyCs?t=43m34s

Thinking In Ecto - Darin Wilson https://www.youtube.com/watch?v=YQxopjai0CU

1. Repository pattern https://youtu.be/YQxopjai0CU?t=2m12s
2. Explicitness https://youtu.be/YQxopjai0CU?t=5m29s

pierrejoubert73

How to add a collapsible section in markdown

1. Example

Click me

Heading

1. Foo
2. Bar
   • Baz

• Qux

alexellis

Additional notes

Original blog post - http://blog.alexellis.io/live-stream-with-docker/

How do I rebuild the image from scratch?

This will take several hours on a Raspberry Pi Zero - but less time on a Pi 2 or Pi 3. You can edit the Dockerfile for a Pi 2/3 and change RUN make to RUN make -j 4 to take advantage of the quad-core processor.

$ git clone https://github.com/alexellis/raspberrypi-youtube-streaming/

mrange

Railway Oriented Programming and F# Result

Full source: https://gist.github.com/mrange/aa9e0898492b6d384dd839bc4a2f96a1

Option<_> is great for ROP (Railway Oriented Programming) but we get no info on what went wrong (the failure value is None which carries no info).

With the introduction F# 4.1 we got Result<_, _> a "smarter" Option<_> as it allows us to pass a failure value.

However, when one inspects the signature of Result.bind one sees a potential issue for ROP:

mmainz

#### basic data types

x = 1
y = 2
x + y

string = "I am a string and a binary!"
binary = <<69, 76, 73, 88, 73, 82, 1>>

charlist = 'I am NOT a string'