v-kolesnikov

ROM-SQL and serialized YAML data

New projects that use rom-db interact with existing db schemas quite often, especially with schemas that are built on top of Rails applications. And you can probably came across to a serialized YAML data here. ActiveRecord provides API to store unstructured key-value data into single database column with serialize method:

# Serialize preferences as Hash using YAML coder.
class User < ActiveRecord::Base
  serialize :preferences, Hash
end

v-kolesnikov

require 'faker'

RSpec.configure do |config|
  config.before do
    ENV['TZ'] = Faker::Address.time_zone
  end
end

v-kolesnikov

# frozen_string_literal: true

# -*- mode: ruby -*-
# vi: set ft=ruby :

script = <<~SCRIPT
  # Update apt and get dependencies
  sudo apt-get update
  sudo DEBIAN_FRONTEND=noninteractive apt-get install -y unzip curl vim \
      apt-transport-https \

v-kolesnikov

{
  "title": "Diamond Cursor",
  "rules": [
    {
      "description": "Change fn + I/J/K/L to Arrow Keys",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "key_code": "i",

v-kolesnikov

Latency Comparison Numbers
--------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD

v-kolesnikov

Keybase proof

I hereby claim:

• I am v-kolesnikov on github.
• I am vasilykolesnikov (https://keybase.io/vasilykolesnikov) on keybase.
• I have a public key ASC0H9O8-epQhr5LRHOY8fxrfvQBqgda5x54cuBnzeOi3Ao

To claim this, I am signing this object:

v-kolesnikov

LLDB Cheat Sheet

A complete gdb to lldb command map.

Print out

• Print object

(lldb) po responseObject
(lldb) po [responseObject objectForKey@"state"]

• p - Print primitive type

v-kolesnikov

require 'rom'
require 'rom-repository'
require 'sqlite3'

rom = ROM.container(:sql, 'sqlite::memory') do |conf|
  conf.default.create_table(:bookings) do
    primary_key :book_ref
  end

  conf.default.create_table(:tickets) do

v-kolesnikov

class Jobs < ROM::Relation[:sql]
  schema(:jobs) do
    # ...

    associations do
      belongs_to :team
      belongs_to :template
      belongs_to :address
      belongs_to :client
    end

v-kolesnikov

Строгость и нищета списков.

Map и структурная рекурсия.

Применить функцию к каждому элементу списка - это просто: ###GHC/Base.lhs

map _ []     = []
map f (x:xs) = f x : map f xs