littlekbt

 articles_table = Article.arel_table

    # subquery
    articles = articles_table
              .project(Arel.star) # project = select
              .where(articles_table[:type].eq('daily'))
                     .or(articles_table[:type].eq('weekly')) # or
                     .and(articles_table[:type].not_eq('monthly')) #!=
                     .and(articles_table[:active].eq(1)) # =
                     .and(articles_table[:created_at].gt(Date.today)) # >

littlekbt

def index(idx, arr)
  # 終了条件
  return p arr[0] if idx == 0

  # 頭１つ落とす
  index idx - 1, arr[1..-1]
end

index 3, [1, 2, 3, 4, 5]

littlekbt

module A
  hoge = "hoge"
  module B
    fuga = "fuga"
    def self.b
      p hoge
    end
    
    def self.c
      p fuga

littlekbt

def dubble(a)
  if a.is_a?(Fixnum)
    result = a * 2
  end
  p result
end

littlekbt

ary = [10, 5, 3, 4, 20, 50, 15]

#配列を受けて二つに割る。
def split_ary(ary, pivot_idx = 0)
    return ary if ary.empty?
    left = []
    right = []
    ary.each_with_index do |val, index|
        next if index == pivot_idx
        if val < ary[pivot_idx]

littlekbt

ary = [10, 5, 3, 4, 20, 50, 15]

#配列を受けて二つに割る。
def split_ary(ary, pivot_idx = 0)
    left = []
    right = []
    pivot = 0
    ary.each_with_index do |val, index|
        next if index == pivot_idx
        if val < ary[pivot_idx]

littlekbt

class Array
  def insert_and_delete(idx, y)
    move_elem = self[idx]
    self.delete_at(idx)
    self.insert(y, move_elem)
  end
end

def insert_sort(arr)
  num_of = arr.size - 1