khusnetdinov

Learning Rust

The following is a list of resources for learning Rust as well as tips and tricks for learning the language faster.

Warning

Rust is not C or C++ so the way your accustomed to do things in those languages might not work in Rust. The best way to learn Rust is to embrace its best practices and see where that takes you.

The generally recommended path is to start by reading the books, and doing small coding exercises until the rules around borrow checking become intuitive. Once this happens, then you can expand to more real world projects. If you find yourself struggling hard with the borrow checker, seek help. It very well could be that you're trying to solve your problem in a way that goes against how Rust wants you to work.

khusnetdinov

(fn [n coll]
  (loop [n n
         coll coll
         acc '()]
    (if (empty? coll)
      (filter #(= n (count coll))(reverse acc)
      (recur n (drop n coll) (conj acc (take n coll))))))

khusnetdinov

---
# SSH server settings, in line with https://stribika.github.io/2015/01/04/secure-secure-shell.html
# Before using, change myhosts to your hosts' nickname and myuser to your username (two instances! make sure you replace both or you'll be locked out of ssh!)
- hosts: myhosts
  become: true
  remote_user: myuser
  tasks:
    # Key exchange, ciphers and MACs
    - lineinfile: dest=/etc/ssh/sshd_config regexp='^KexAlgorithms' line='KexAlgorithms curve25519-sha256@libssh.org,diffie-hellman-group-exchange-sha256'
    

khusnetdinov

# frozen_string_literal: true

require 'i18n/tasks'

RSpec.describe 'I18nEnsurance' do
  let(:i18n) { I18n::Tasks::BaseTask.new }
  let(:missing_keys) { i18n.missing_keys }
  let(:unused_keys) { i18n.unused_keys }

  it 'does not have missing keys' do

khusnetdinov

SELECT
    pg_class.relname,
    pg_size_pretty(pg_class.reltuples::BIGINT) AS rows_in_bytes,
    pg_class.reltuples AS num_rows,
    COUNT(indexname) AS number_of_indexes,
    CASE WHEN x.is_unique = 1 THEN 'Y'
       ELSE 'N'
    END AS UNIQUE,
    SUM(CASE WHEN number_of_columns = 1 THEN 1
              ELSE 0

khusnetdinov

SELECT pg_size_pretty(SUM(pg_relation_size(idx))::BIGINT) AS SIZE,
       (array_agg(idx))[1] AS idx1, (array_agg(idx))[2] AS idx2,
       (array_agg(idx))[3] AS idx3, (array_agg(idx))[4] AS idx4
FROM (
    SELECT indexrelid::regclass AS idx, (indrelid::text ||E'\n'|| indclass::text ||E'\n'|| indkey::text ||E'\n'||
                                         COALESCE(indexprs::text,'')||E'\n' || COALESCE(indpred::text,'')) AS KEY
    FROM pg_index) sub
GROUP BY KEY HAVING COUNT(*)>1
ORDER BY SUM(pg_relation_size(idx)) DESC;

khusnetdinov

SELECT
  current_database(), schemaname, tablename, /*reltuples::bigint, relpages::bigint, otta,*/
  ROUND((CASE WHEN otta=0 THEN 0.0 ELSE sml.relpages::FLOAT/otta END)::NUMERIC,1) AS tbloat,
  CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::BIGINT END AS wastedbytes,
  iname, /*ituples::bigint, ipages::bigint, iotta,*/
  ROUND((CASE WHEN iotta=0 OR ipages=0 THEN 0.0 ELSE ipages::FLOAT/iotta END)::NUMERIC,1) AS ibloat,
  CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes
FROM (
  SELECT
    schemaname, tablename, cc.reltuples, cc.relpages, bs,

khusnetdinov

-- WARNING: executed with a non-superuser role, the query inspect only index on tables you are granted to read.
-- WARNING: rows with is_na = 't' are known to have bad statistics ("name" type is not supported).
-- This query is compatible with PostgreSQL 8.2 and after
SELECT current_database(), nspname AS schemaname, tblname, idxname, bs*(relpages)::bigint AS real_size,
  bs*(relpages-est_pages)::bigint AS extra_size,
  100 * (relpages-est_pages)::float / relpages AS extra_ratio,
  fillfactor, bs*(relpages-est_pages_ff) AS bloat_size,
  100 * (relpages-est_pages_ff)::float / relpages AS bloat_ratio,
  is_na
  -- , 100-(sub.pst).avg_leaf_density, est_pages, index_tuple_hdr_bm, maxalign, pagehdr, nulldatawidth, nulldatahdrwidth, sub.reltuples, sub.relpages -- (DEBUG INFO)

khusnetdinov

$ brew install libmagic
$ brew link libmagic  (if the link is already created is going to fail, don't worry about that)
$ env ARCHFLAGS="-arch x86_64" gem install ruby-filemagic -- --with-magic-include=/usr/local/include --with-magic-lib=/usr/local/lib/

khusnetdinov

1. Знание основ Ruby, фреймворка Ruby on Rails
 - http://guides.rubyonrails.org/
 - http://rusrails.ru/
 Вопросы:
 1. Чем отличается статическая и динамическая типизации в языках программирования?
 2. Какие виды наследования поддерживаются в Ruby?
 3. Что такое модуль? Какая разница между классом и модулем?
 4. Какие есть уровни контроля доступа к методам для классов и модулей?
 5. Какие есть способы вызова методов в Ruby?
 6. Что означает ключевое слово self?