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EncodePanda / TwoThreeTree.hs
Last active Nov 21, 2021
First attempt to implement 2-3 tree as outlined in the "Finger Trees: A Simple General-purpose Data Structure" paper
View TwoThreeTree.hs
-- λ> fromList [1]
-- Zero 1
-- λ> fromList [1..2]
-- Succ (Zero (Node2 1 2))
-- λ> fromList [1..4]
-- Succ (Succ (Zero (Node2 (Node2 1 2) (Node2 3 4))))
-- λ> fromList [1..8]
EncodePanda /
Last active Sep 7, 2020
Functional Dependencies dilemma

hi all, I'm trying to get my head around functional dependencies I've created a simplified version of MonadReader that has no functional dependencies

class MyMonadReader r m where
  ask :: m r

What works as expected

When creating instances like

View osx-setup-notes.txt
Pawel Szulc
Table of Contents
1 Install Nix
2 Install Brew :(
3 Zsh and Oh my zsh
.. 3.1 Install zsh and zsh-completions

Since macOS Catalina, the root drive is read-only. The solution is to create a separate APFS volume and a “synthetic” /nix directory which points to it:

# Check if /nix exists, if not:
echo 'nix' | sudo tee -a /etc/synthetic.conf
# this will create a "synthetic" empty directory /nix

# REBOOT so macOS sees the synthetic directory

# After rebooting, create an APFS volume for Nix
View nix issue
nix-shell --pure --show-trace
building '/nix/store/dkmy7cp9dqb2xqnjx1x3lgarn5y2kv07-all-cabal-hashes-component-stylish-haskell-'...
tar: */stylish-haskell/ Not found in archive
tar: */stylish-haskell/ Not found in archive
tar: Exiting with failure status due to previous errors
builder for '/nix/store/dkmy7cp9dqb2xqnjx1x3lgarn5y2kv07-all-cabal-hashes-component-stylish-haskell-' failed with exit code 2
cannot build derivation '/nix/store/d9281ziwi2rkfrk40w1y55krxym43p93-cabal2nix-stylish-haskell-': 1 dependencies couldn't be built
error: while evaluating the attribute 'buildInputs' of the derivation 'ghc-shell-for-packages' at /nix/store/zrz1pihi0blg5mzchv19agqkjxd2vlag-nixos-release-19.03/pkgs/development/haskell-modules/make-package-set.nix:301:9:
while evaluating 'getOutput' at /nix/store/zrz1pihi0blg5mzchv19agqkjxd2vlag-nixos-release-19.03/lib/attrsets.nix:464:23, called from undefined position:
while evaluating anon
View stylish-conf.yaml
# stylish-haskell configuration file
# ==================================
# The stylish-haskell tool is mainly configured by specifying steps. These steps
# are a list, so they have an order, and one specific step may appear more than
# once (if needed). Each file is processed by these steps in the given order.
# Convert some ASCII sequences to their Unicode equivalents. This is disabled
# by default.
# - unicode_syntax:
View try_postgresql_simple.hs
{-# LANGUAGE DeriveAnyClass #-}
{-# LANGUAGE DeriveGeneric #-}
{-# LANGUAGE OverloadedStrings #-}
module Main where
import Control.Applicative
import Control.Monad
import Database.PostgreSQL.Simple
import GHC.Generics (Generic)
View free from scratch.hs
{-# LANGUAGE KindSignatures #-}
module Lib where
data Console k =
Done k |
PrintLine String (Console k) |
ReadLine (String -> Console k)
instance Functor Console where
fmap f (Done a) = Done (f a)
View tla+

"Specifiing distributed systems with TLA+"

Elevator pitch:

Learn how to use TLA+ to study, design and specify your algorithms. This workshop is designed to teach you about TLA+ from the ground up. We will start with simple distributed algorithms and slowly move toward more complex ones. Knowledge you gain can be immediatly applied at work next day after the workshop


TLA+ is a formal specification language developed by Leslie Lamport, designed to specify, model, document, and verify concurrent systems. It empowers your ability to clearly specify your design choices in the form of a formal specification, but also (even more importantly) can formally verify that your design choice is correct—meaning that it is both safe (does not break any rules) and live (over time it converges toward the result).

View gist:ad2fe6a4fe5f52a5fe2560ec04f851c6
rn_stop() {
echo "stop all existing rnode processes"
kill $(ps aux | grep '[r]node' | awk '{print $2}')
rn_clean() {
echo "clean .rnode folders"
echo ~/.rnode*
rm -rf ~/.rnode*
echo "create bootstrap rnode folder"