edolstra

General notes

• nix-channel and ~/.nix-defexpr are gone. We'll use $NIX_PATH (or user environment specific overrides configured via nix set-path) to look up packages. Since $NIX_PATH supports URLs nowadays, this removes the need for channels: you can just set $NIX_PATH to e.g. https://nixos.org/channels/nixos-15.09/nixexprs.tar.xz and stay up to date automatically.

• By default, packages are selected by attribute name, rather than the name attribute. Thus nix install hello is basically equivalent to nix-env -iA hello. The attribute name is recorded in the user environment manifest and used in upgrades. Thus (at least by default) hello won't be upgraded to helloVariant.

  @vcunat suggested making this an arbitrary Nix expression rather than an attrpath, e.g. firefox.override { enableFoo = true; }. However, such an expression would not have a key in the user environment, unlike an attrpath. Better to require an explicit flag for this.

TBD: How to deal with search path clashes.

3noch

module Geoposition where

import           Control.Concurrent (forkIO)
import           Control.Monad.Exception (catch, throw)
import           Control.Monad.IO.Class (liftIO)

import           Reflex (Event)
import           Reflex.Dom (MonadWidget)
import           Reflex.Dom.Class (performEventAsync)

carlessanagustin

Nginx Cheat Sheet

(from Understanding Nginx Server and Location Block Selection Algorithms - https://goo.gl/YyzshP)

• Alphabetical index of directives
• Alphabetical index of variables
• Documentation

server {

vasanthk

System Design Cheatsheet

Picking the right architecture = Picking the right battles + Managing trade-offs

Basic Steps

1. Clarify and agree on the scope of the system

• User cases (description of sequences of events that, taken together, lead to a system doing something useful)
  • Who is going to use it?
  • How are they going to use it?

roelvandijk

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE PolyKinds #-}
{-# LANGUAGE ScopedTypeVariables #-}
{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE TypeOperators #-}
{-# LANGUAGE UndecidableInstances #-}
module Nub where

import Data.Proxy
import Data.Type.Bool

martijnvermaat

Installation of NixOS with encrypted root

These are my notes on instaling NixOS 16.03 on a Lenovo ThinkPad X1 Carbon (4th generation) with an encrypted root file system using UEFI.

Most of this is scrambled from the following pages:

• Encrypted Root on NixOS - Nix Wiki
• Installing NixOS - Chris Martin
• Linux administration and use - Earl Douglas
• Installing NixOS on a ThinkPad W540 with encrypted root - Bluish Coder

aisamanra

module Main where

{-
Here is a real---if not particularly interesting---interaction with this server:

  [gdritter@armilla ~]$ ssh -p 9999 localhost incr
  ok.
  [gdritter@armilla ~]$ ssh -p 9999 localhost incr
  ok.
  [gdritter@armilla ~]$ ssh -p 9999 localhost double

phadej

{-# LANGUAGE DataKinds              #-}
{-# LANGUAGE FlexibleInstances      #-}
{-# LANGUAGE FunctionalDependencies #-}
{-# LANGUAGE KindSignatures         #-}
{-# LANGUAGE MultiParamTypeClasses  #-}
{-# LANGUAGE PolyKinds              #-}
{-# LANGUAGE RankNTypes             #-}
{-# LANGUAGE ScopedTypeVariables    #-}
{-# LANGUAGE TypeFamilies           #-}
{-# LANGUAGE TypeSynonymInstances   #-}

Icelandjack

Reddit discussion.

Disclaimer 1: Type classes are great but they are not the right tool for every job. Enjoy some balance and balance to your balance.

Disclaimer 2: I should tidy this up but probably won’t.

Disclaimer 3: Yeah called it, better to be realistic.

Type classes are a language of their own, this is an attempt to document features and give a name to them.

3noch

# This expression builds a copy of Twitter Bootstrap CSS but with every rule embedded inside a CSS selector of
# your choice. This makes it easy to embed a Bootstrap-themed component in a site that doesn't use Bootstrap.
#
# Usage
#   * Install nix from https://nixos.org/nix/ (it's a fancy package manager that won't mess up your system)
#   * Save this file to `scoped-bootstrap.nix`
#   * With nix stuff on your PATH, run `nix-build scoped-bootstrap.nix`
#   * The result will be in `./result/` (a symlink). Copy to desired location.
#   * If you don't want to keep `nix`: `rm -rf /nix`