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%w(Chapman Cleese Gilliam) ** %w(ham egg spam)
#=>
[["Chapman", "ham"], ["Chapman", "egg"], ["Chapman", "spam"],
["Cleese", "ham"], ["Cleese", "egg"], ["Cleese", "spam"],
["Gilliam", "ham"], ["Gilliam", "egg"], ["Gilliam", "spam"]]

%w(Chapman Cleese Gilliam).combination(2).to_a
#=> [["Chapman", "Cleese"], ["Chapman", "Gilliam"], ["Cleese", "Gilliam"]]

%w(k t k r).pad(10, "!")
#=> ["k", "t", "k", "r", "!", "!", "!", "!", "!", "!"]

["Crosby", "Stils", "Nash", "Young"].conjoin(', ', ' & ')
#=> "Crosby, Stils, Nash & Young"

arr = (1..100).to_a
class << arr
  include Denumerable
end
puts arr.select{|n| n%10==0}.map{|n| n**2}.to_a

(1970..1990).group_by{|y| y < 1989 ? 'showa' : 'heisei' }
#=>
{"heisei"=>[1989, 1990],
"showa"=>[1970, 1971, 1972, 1973, 1974, 1975, 1976, 1977, 1978, 1979, 1980, 1981, 1982, 1983, 1984, 1985, 1986, 1987, 1988]}

[:year, :month, :day].mash{|sym| [sym, Date.today.send(sym)]}
#=> {:day=>24, :month=>12, :year=>2009}

%w(ham egg spam egg spam egg).mode #=> ["egg"]

%w(ham egg spam egg spam egg).probability
#=> {"egg"=>0.5, "spam"=>0.333333333333333, "ham"=>0.166666666666667}

%w(ham egg spam egg spam egg).frequency
 #=> {"egg"=>3, "spam"=>2, "ham"=>1}

%w(ham egg ham egg ham egg).entropy #=> 1.0
%w(ham egg ham egg ham spam).entropy #=> 1.45914791702724
%w(ham egg spam! egg ham spam).entropy #=> 1.91829583405449
%w(ham egg spam! spam!! ham spam).entropy #=> 2.25162916738782
%w(ham egg spam! spam!! spam!!! spam).entropy #=> 2.58496250072116
%w(spam!!!! egg spam! spam!! spam!!! spam).entropy #=> 2.58496250072116
%w(spam!!!! spam!!!!! spam! spam!! spam!!! spam).entropy #=> 2.58496250072116

{ :john=>'lennon'} + { :ono=>'yoko'} #=> {:john=>"lennon", :ono=>"yoko"}
{ :john=>'lennon', :ono=>'yoko'} - { :john=>'lennon'} #=> {:ono=>yoko}
{ :john=>'lennon', :ono=>'yoko'}.join(' ', ', ') #=> "john lennon, ono yoko"

class Monty
  def initialize(name); @name = name end
end
%w(Chapman Cleese Gilliam).map &Monty
 
 #=> [#<Monty:0x1254a6c @name="Chapman">,
 #<Monty:0x1254a30 @name="Cleese">,
 #<Monty:0x12549f4 @name="Gilliam">]

d variable
#=> [["Chapman", "Cleese", "Gilliam", "Idle", "Jones", "Palin"]] d.rb:5

me = "tomoya55"
monties = ["Chapman", "Cleese", "Gilliam", "Idle", "Jones", "Palin"]
me.in? monties #=> false

ask "Oops, I encoutered unexpected problems. Do you want to debug me?"

loop do
  break if maybe
end

# Christmas Eve by Tasturo Yamashita
maybe(0.01) ? 'she will come' : 'she will not'

silently do
  warn "It is a Chiristmas, stupid!"
  puts "We wish a Merry Chiristmas, We wish a Merry Chiristmas"
  STDERR.puts "****, explode!"
end

alias devnull silently

str = "0123456"
class << str
  include Stackable
end
str.pop #=> 6
str.push("9") #=> "0123459"

Time.elapse{require 'active_support'} #=> 0.695170879364014
Time.elapse{require 'extlib'} #=> 0.185311079025269

Time.now.ago(1, :years)

Time.now.advance(:years=>1)

class ChristmasObject
  wrap(:inspect) do |orig, *args|
    "<We Wish>" + orig.call + "< a Merry Christmas!!>"
  end
end
p ChristmasObject.new #=> <We Wish>#<ChristmasObject:0x12535cc>< a Merry Christmas!!>

:friend.not? #=> false
:'~friend'.not? #=> true

"ero".bracket('(') #=> "(ero)"
"ero".bracket('x') #=> "xerox"
"santa".chars #=> ["s", "a", "n", "t", "a"]
"santa clause".cleave #=> ["santa", "clause"] cleaveは「割く」という意味ぽい
 
%q(/usr/bin/ruby).quote(:b) #=> "`/usr/bin/ruby`"
%q(/usr/bin/ruby).quote(:s) #=> "'/usr/bin/ruby'"
%q(/usr/bin/ruby).quote(:d) #=> ""/usr/bin/ruby""
%q("/usr/bin/ruby").dequote #=> "/usr/bin/ruby"
 
"ham spam".rewrite([[/am/, "i"],[/\s/,'-']]) #=> "hi-spi"