Dan Janowski danj3

A digital craftsman, coder, system architect, sherpa

danj3 / terms.exs

Created December 10, 2025 18:20

elixir, parse a string term, emit a string term

	string_to_term = fn string ->
	string
	\|> String.to_charlist()
	\|> :erl_scan.string()
	\|> then(fn {:ok, term, _} -> :erl_parse.parse_term(term) end)
	end

	term_to_string = fn term ->
	:io_lib.format("~w.", [term]) \|> :erlang.iolist_to_binary()
	end

danj3 / gist:5da5461acde4723bedc6d33cf9b0e953

Created September 2, 2025 16:00

	# Build And Package

	Live meeting 2sep 25

	# Priority issues rebar3

	1. issues with using hex deps to compile
	2. locking of plugins for non default profiles
	3. windows may be broken, CI says it is but that may only be CI
	4. relx on windows is in a questionable state

danj3 / silly-macros.livemd

Created July 29, 2025 19:44

Example of macros and use of explicit variables vs magic variables

Silly Macros

Mix.install([
  {:kino, "~> 0.16.0"}
])

danj3 / elmdb_stage.ex

Created March 26, 2018 17:45

Elixir: GenStage producer from an :elmdb (LMDB) database using a cursor for linear sequence

	defmodule ElmdbStage do
	@moduledoc """
	Create a GenStage for an :elmdb based LMDB database cursor.
	This is for linearly reading from a db
	"""
	use GenStage

	def start_link( env, db ) do
	GenStage.start_link( __MODULE__, { env, db } )
	end

danj3 / hash_signature.ex

Last active March 26, 2018 14:30

Elixir: create an armored sha256 hash of an input

	defmodule HashSignature do
	@doc """
	encode input to a sha256 and output as an armored string.
	results should be fully portable and consistent with other
	tools.
	"""
	def get( input ) do
	:crypto.hash( :sha256, input )
	\|> :crypto.bytes_to_integer
	\|> (fn i -> :io_lib.format("~64.16.0b",[i]) \|> hd end ).()

danj3 / time_agent.ex

Created March 26, 2018 13:25

Elixir agent for active tracking execution time

	defmodule TimeAgent do

	def start_link do
	Agent.start_link( fn -> { Map.new, Map.new } end, name: __MODULE__ )
	end

	def time_run( m, f, a ) do
	{ us, result } = :timer.tc( m, f, a )
	Agent.cast( __MODULE__, __MODULE__, :add_sample, [ to_string(m) <> "." <> to_string(f), us ] )
	result

danj3 / term_round_trip.exs

Created March 15, 2018 00:34

Elixir: example of turning a term to a string and a string to a term

	defmodule TermRoundTrip do
	@moduledoc """
	Convert a term to a readable string then back to a term
	"""

	def term_to_binary( term ) do
	:io_lib.format("~p.~n", [ term ] )
	\|> :erlang.iolist_to_binary
	end

danj3 / day4.ex

Created December 19, 2017 04:53

Advent of Code (AOC) 2017 Day 4

	defmodule Day4 do
	def parser( input ) do
	String.split( input, "\n" )
	\|> Enum.reduce( [], fn "", acc -> acc; line,acc -> [ String.split(line," ") \| acc ] end )
	end

	def start1( input ) do
	parser( input ) \|> step1a( [valid: 0, invalid: 0] )
	end

danj3 / day3.ex

Created December 15, 2017 14:00

Advent of Code (AOC) 2017 Day 3

	defmodule Day3 do
	# This does more work than required but is still O(1)
	# diagonal low right is even square root
	def start1( val ) do
	col_height = :math.sqrt( val ) \|> Float.ceil \|> trunc
	col_height = if Integer.mod( col_height, 2 ) == 0, do: col_height+1, else: col_height
	low_right_corner = :math.pow( col_height, 2 ) \|> trunc
	distance = low_right_corner - val
	ring_length = col_height * 4 - 4

danj3 / day2.ex

Created December 12, 2017 01:41

Advent of Code 2017 Day 2