d11wtq

Comparing the power and expressiveness of various database query systems

Simple select all.

SELECT * FROM users;

User.all

d11wtq

# foldl() is fundamental. With a fold, you can do everything else.
def foldl(list, acc, &fn)
  if list == [] # base case, return the accumulator
    acc
  else
    head, *tail = list
    foldl(tail, fn.call(acc, head), &fn) #recurse on the remainder
  end
end

d11wtq

%% @doc This implements a kitchen fridge that you can put things into
%%      and take them out.
%%
%% It is stateful, through the use of recursion.
%% I opted for the sets module only because I wanted to try it.
%% Using the sets module has the side-effect that you can only store
%% one of each food item in the fridge.
-module(kitchen).
-export([new/0, store/2, take/2]).

d11wtq

%% @doc Reverse Polish Notation Calculator.
%%
%% Parses expressions like "1 2 3 + -" = -4
%%
%% This is an exercise in Learn You some Erlang for Great Good,
%% however I didn't read the text and just implemented it.
%%
%% I guess understanding stack-based parsing helps here.
-module(calc).
-export([rpn/1]).

d11wtq

%% @doc A binary tree implementation in Erlang.
%%      A binary tree stores keys and values.

-module(binary_tree).
-export([init/0, init/1, insert/3, lookup/2]).
-define(EMPTY_NODE, {node, 'empty'}).

%% @doc Initialize an empty binary tree node.
%%      This is how the root of the tree should be established.
%%

d11wtq

class Time
  class << self
    attr_accessor :mock_time

    def now_with_mock_time
      @mock_time || now_without_mock_time
    end

    alias_method_chain :now, :mock_time

d11wtq

class Sidekiq::Middleware::Server::GC
  def call(worker, msg, queue)
    yield
  ensure
    GC.start
  end
end

d11wtq

class AnsiColorTest
  FG = 38
  BG = 48

  class << self
    def label(n, type)
      "\033[01;#{type};5;#{n}m     %3s     \033[0m" % n
    end

    def dump256

d11wtq

/*
 Assuming you have an enum type like this.
 You want to rename 'pending' to 'lodged'
 */
CREATE TYPE dispute_status AS ENUM('pending', 'resolved', 'open', 'cancelled');

BEGIN;

  ALTER TYPE dispute_status ADD VALUE 'lodged';
  UPDATE dispute SET status = 'lodged' WHERE status = 'pending';

d11wtq

module DataMapper
  class Transaction
    def link_with_master_slave(*things)
      things = things.collect do |t|
        case t
        when DataMapper::Adapters::MasterSlaveAdapter
          t.master
        else
          t
        end