Anders Christiansen Sørby Anderssorby

Problem

You have installed GPG, then tried to perform a git commit and suddenly you see this error message after it 😰

error: gpg failed to sign the data
fatal: failed to write commit object

Understand the error (important to solve it later!)

Optics By Example Cheat Sheets

The following are appendices from Optics By Example, a comprehensive guide to optics from beginner to advanced! If you like the content below, there's plenty more where that came from; pick up the book!

Operators
Composition Guide
Substitution Guide
Optical Constarints and Types

Operator Cheat Sheet

Basic QTT

Quantitative type theory (QTT) is an extension of dependent type theory which allows us to track the number of computational (non-erased) uses of variables in well-typed lambda terms. With such usage information, QTT allows us to combine dependent types with substructural types, such as linear, affine or relevant types.

While in a Martin-Löf style type theory typing judgments are of form x1 : A1, ..., xn : An ⊢ b : B, in QTT the bindings in the context

	package bar.foo.lenses;

	import java.util.function.BiFunction;
	import java.util.function.Function;

	public class Lens<A, B> {

	private final Function<A, B> getter;
	private final BiFunction<A, B, A> setter;

	"""
	Minimal character-level Vanilla RNN model. Written by Andrej Karpathy (@karpathy)
	BSD License
	"""
	import numpy as np

	# data I/O
	data = open('input.txt', 'r').read() # should be simple plain text file
	chars = list(set(data))
	data_size, vocab_size = len(data), len(chars)

	""" Trains an agent with (stochastic) Policy Gradients on Pong. Uses OpenAI Gym. """
	import numpy as np
	import cPickle as pickle
	import gym

	# hyperparameters
	H = 200 # number of hidden layer neurons
	batch_size = 10 # every how many episodes to do a param update?
	learning_rate = 1e-4
	gamma = 0.99 # discount factor for reward

	mkfs.vfat -n BOOT /dev/sda1
	mkfs.btrfs -L root /dev/sda2

	mount -t btrfs /dev/sda2 /mnt/
	btrfs subvolume create /mnt/nixos
	umount /mnt/
	mount -t btrfs -o subvol=nixos /dev/sda2 /mnt/
	btrfs subvolume create /mnt/var
	btrfs subvolume create /mnt/home
	btrfs subvolume create /mnt/tmp

	{config, pkgs, ...}:
	{

	# Enable Nginx
	services.nginx = {
	enable = true;

	# Use recommended settings
	recommendedGzipSettings = true;
	recommendedOptimisation = true;