Day 2 ~ 13： Ruby 認定試験による勉強

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# 1. coding: us-ascii
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# 2. encoding: us-ascii
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# 3. -*- charset: us-ascii -*-
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# 4. CODING: US-ASCII

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begin
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# 例外が起こりうるコード1
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rescue => # 変数(例外オブジェクトの代入)
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# 例外が起きた場合のコード2
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ensure
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# 例外の有無に関わらず、実行するコード3
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end

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MAX=10
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print MAX
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MAX=100
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print MAX

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def foo(*a)
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  p a
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end
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foo(1,2,3)
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#実行結果 [1,2,3]

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def sum (##AAA##)
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  total = 0
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  a.each {|i| total += i }
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  return total
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end
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puts sum(1, 2, 3, 4, 5)
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=>15

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#引数baseを取ることもでき、その引数で何進数かを示す。
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#デフォルト値は10であり、引数指定しない場合は10進数となる。
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変数.to_i(2)

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def hoge
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  x = 0
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  (1...5).each do |i|
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    x += 1
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  end
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  puts x
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end
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hoge
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#実行結果 4

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#範囲オブジェクト等：問題
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a = [1,2,3,4]
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#ここに代入する式を選択して下さい。
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a.each do |i|
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  print i, " "
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end
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#実行結果
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1 2 3
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# 選択肢
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1: a[0..3], 2: a[0..-2], 3: a[0...-2], 4: a[0...-3],
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5: a[3,0], 6: a[0,3], 7: a[2,0], 8: a[0,2]
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# 答えは2と6

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money = 1000
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オブジェクト.upto(max) do |i|
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  実行処理
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end
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money = 100
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1.upto(3) do |i|
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  money = money * 1.1
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end
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puts money.to_i

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オブジェクト.step(limit, stepno) do |変数|
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  実行する処理1
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  実行する処理2
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end

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money = 1000
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rate = 1.1
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2001.upto(2004) do |i|
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  money = money * rate
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  puts "I got #{money.to_i} in #{i}."
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end
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#実行結果
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# I got 1100 in 2001.
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# I got 1210 in 2002.
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# I got 1331 in 2003.
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# I got 1464 in 2004.

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money = 1000
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rate = 1.1
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(2001..2004).each do |i|
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  money *= rate
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  puts "I got #{money.to_i} in #{i}."
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end

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class User
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  attr_accessor:say
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  def initialize
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    @say = "Hello"
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  end
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end
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class Oriver < User
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  def initialize
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    super
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  end
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end
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oriver = User.new
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puts oriver.say
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#実行結果：Hello
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#この時、superメソッドは親クラスのUserから、@sayを呼び出している

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#円の面積
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include Math
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def area r
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  return r * r * PI
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end
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#球の体積
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def volume r
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  return (4/3) * r * r * r * PI
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end
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#πの値
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puts PI #結果：3.141592653589793
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area(2) #結果：12.566370614359172
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volume (2)  : 25.132741228718345

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# 二項演算子
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def +(other) # obj + other
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def -(other) # obj - other
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# 単項プラス/マイナス
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def +@ # +obj
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def -@ # -obj
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# 要素代入
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def foo=(value) # obj.foo = value
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# [] と []=
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def [](key) # obj[key]
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def []=(key, value) # obj[key] = value
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def []=(key, key2, value) # obj[key, key2] = value
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# バッククォート記法
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def `(arg) # `arg` または %x(arg)

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##比較演算子と<<  ：問題
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class Employee
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  attr_reader :id
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  attr_accessor :name
5

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  def initialize id, name
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    @id = id
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    @name = name
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  end
10

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  def to_s
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    return "#{@id}:#{@name}"
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  end
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#ここに代入する式を選択して下さい。
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end
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employees = []
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employees << Employee.new("3","Tanaka")
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employees << Employee.new("1","Suzuki")
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employees << Employee.new("2","Sato")
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employees.sort!
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employees.each do |employee| puts employee end
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# 実行結果
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1:Suzuki
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2:Sato
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3:Tanaka
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# 選択肢
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# 1 (答え）
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def <=> other
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  return self.id <=> other.id
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end

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#例
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animals = ["dog", "cat", "mouse"]
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animals << "pig"
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p animals
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["dog", "cat", "mouse", "pig"]

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#問題
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a = [1,2,3,4]
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b = [1,3,5,7]
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#ここに代入する式を選択して下さい。
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c = XXXX
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c.each {|i| print i, " " }
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#出力結果
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1 3
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#選択肢
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1: a+b, 2: a-b, 3: a & b, 4: a && b, 5: a | b, 6: a || b
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#解答 3

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#select
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[1, 2, 3, 4, 5].select{ |v| v % 2 == 1 }
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=> [1, 3, 5]
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#find_all
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[1, 2, 3, 4, 5].find_all{ |v| v % 2 == 1 }
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=> [1, 3, 5]

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#map
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[1, 2, 3, 4, 5].map{ |v| v % 2 == 1 }
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=> [true, false, true, false, true]
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#collect
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[1, 2, 3, 4, 5].collect{ |v| v % 2 == 1 }
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=> [true, false, true, false, true]

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#find
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[1, 2, 3, 4, 5].find{ |v| v % 2 == 1 }
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=> 1

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val = [ "a", "b" ]
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c=> ["a", "b"]
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val.concat( ["c", "d"] ) #=> [ "a", "b", "c", "d" ]
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=> ["a", "b", "c", "d"]l
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puts val
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a
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b
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c
9
d

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a1=%w(a b)
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a2=%w(x y)
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a3=a1.zip(a2)
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p a3.first
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# 選択肢
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1: "a", 2: ["a"], 3: ["a", "x"], 4: ["a", "b"], 5. 例外が発生する。
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# 解答

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arr1 = [1, 2, 3]
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arr2 = [4, 5]
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arr3 = [6, 7, 8, 9]
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p arr1.zip(arr2, arr3)
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[[1, 4, 6], [2, 5, 7], [3, nil, 8]]

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a = ["a", "b", "c"]
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b = [1, 2, 3]
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##AAA##
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#実行結果
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["a", 1]
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["b", 2]
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["c", 3]
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#選択肢
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a.zip(b).each{|x| p x }
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a.zip(b){|x| p x }
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[a, b].zip{|x, y| p [x, y] }
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[a, b].transpose.each{|x, y| p [x, y] }
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#答え 1，2，4

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a = [1,2,3,4,5]
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p a.slice(1,3)
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#答え

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a = "abc"
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b = "abc"
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print a.eql? b
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print a.equal? b
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print a == b
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# =>
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# true false true

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s1 = "Hoge"
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s2 = "Fuga"
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s1.concat(s2)
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s1.chop
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s1.chomp
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s1 + s2
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puts s1
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# => ?

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# irb
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s1 = "Hoge"
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s2 = "Fuga"
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s1.concat(s2)
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# .c=> "HogeFuga"
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# chopでs1末尾のeが取り除かれる
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s1.chop
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# => "HogeFug"
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# s1に改行文字は含まれていない
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s1.chomp
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# => "HogeFuga"
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# 文字型同士の和は可能
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s1 + s2
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# => "HogeFugaFuga"
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# concatの破壊的性質により、s1.concat(s2)の時点で、s1がHogeFugaに。
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puts s1
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# HogeFuga

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s = "123456789"
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p s[1,4]
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# =>
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# "2345"

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member = [10, "Tanaka"]
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print "ID:%2d Name:%s" #ここに代入する式を選択して下さい。
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member
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# 実行結果
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ID:10 Name:Tanaka
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# 選択肢
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1: , ,2. +
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3. % ,4. .format
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#答え %

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#{} の問題
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v = {}
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v.class
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#出力答え Hash

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#invert array : 問題
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v = {:v1 => 1, :v2 => v}
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v.invert
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#出力答え {1=>:v1, nil=>:v2}

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sprintf("%d", 4);
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=> "4"
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# %2d 2桁の文字列を返す
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sprintf("%2d", 4);
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=> " 4"
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# %02d 2桁の文字列を返す。桁数が足りない場合は、前に0を追加。
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sprintf("%02d", 4);
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=> "04"

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# ファイルdataの内容はabcdefg
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File.open("data") do |io|
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  while not io.eof?
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    print io.read(1)
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    io.seek(0,IO::SEEK_SET)
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  end
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end
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#答え: aが表示され続ける

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# 問題
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t = Time.gm(1970,1,1)
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puts t.strftime("#ここに代入する式を選択")
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# => 1970/01/01
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#選択肢
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1, %y/%m/%d ,2, %Y/%M/%d
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3, %y/%M/%d ,4, %Y/%m/%d
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#答え：4

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# 問題
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while rand
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goto class const
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#答え whileとclass

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# 問題
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x = 0
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[1,2,3].each do |x|
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 print x.to_s + " "
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end
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puts x
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#解答 1 2 3 0
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# 1，2，3は表示上は数字型だか、実は文字型

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x = 0
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[1,2,3].each do |x|
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  print x.to_s + " "
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  print x.to_s.class
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end
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puts x
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# =>
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# x = 0
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[1,2,3].each do |x|
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  print x.to_s + " "
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  print x.to_s.class
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  o_s.class
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end
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puts x
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# 0
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# => nil

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#問題
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nil 0 "" false 0.0 NULL
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#解答 nil と false

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# 問題
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y = false
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y ##AAA## (raise "failed")
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puts("succeeded!")
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#選択肢
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1, |  ,2, || ,3, & ,4, &&
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#答え &&

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# 問題
2
HOGE = "hoge"
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HOGE.gsub!("hoge", "piyo")
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print HOGE
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# 答え  警告は発生せず、「piyo」が表示される。

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# 問題
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begin
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  puts 10 / 0 #ZeroDivisionError
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  ##AAA##
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  print "ZeroDivisionException:", ex.message
6
end

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begin
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  puts "hello"
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  puts 10 / 0
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  rescue ZeroDivisionError => ex
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    puts "good bye"
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    print "ZeroDivisionException:", ex.message
13
end

1
begin
2
  puts "hello"
3
  puts 10 / 0
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  puts "good afternoon"
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  rescue Exception => ex
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    puts "good bye1111111"
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    print "message:", ex.message
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  rescue ZeroDivisionError => ex
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    puts "good bye2222222"
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    print "ZeroDivisionException:", ex.message
16
end

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# 問題
2
p ?A
3

4
#答え "A"

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#コード１
2
p "A".ord
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# => 65
4

5
#コード２
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p 65.chr
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#=> "A"

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# エラーにならないものを選べ
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class Hoge < Object ; end
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class Hoge << Object ; end
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class Hoge < Kernel ; end
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class Hoge << Kernel ; end
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# A １のみ

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Kernel.call
2
=>Module

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p "12abc".to_i =>123
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p "abc12".to_i =>0
3
p "ab12c".to_i =>0
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p "1abc2".to_i =>`1

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s = "a;b:c;d:e;f"
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p s.split (/:|;/)
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=>["a", "b", "c", "d", "e", "f"]

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p "abc def 123 ghi 456".scan(/\d+/).length
2
=> 2

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a=[1,2,3,4]
2

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a[1,3] => [2,3,4]
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a[1..3] => [2,3,4]
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a[1...3] => [2,3]
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a[1....3] => error
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a[2..-1] => [3,4]

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a="abcdefghijk"
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a[1,3] = "x"
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p a # => "axefghijk"
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a[1..3] = "x"
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p a # => "axefghijk"
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a[1...3] = "x"
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p a # => "axdefghijl"

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a = [1,2,3,4]
2
b = [1,3,5,7]
3

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p a & b =>[1, 3]
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p a && b =>[1, 3, 5, 7]
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p a | b =>[1, 2, 3, 4, 5, 7]
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p a || b =>[1, 2, 3, 4]

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a= [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
2
a.delete_if{|v| v % 2 == 0 }
3
=>[1, 3, 5, 7, 9]
4
p a => [1, 3, 5, 7, 9]

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a = ["apple", "orange", "grape", "pine"]
2
a.each_with_index{ |item, i| print i, ":", item, "\n" }
3
=>
4
0:apple
5
1:orange
6
2:grape
7
3:pine

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s = ["one","two","three"]
2

3
s.shift => "one" ※先頭のoneを削除
4
s.shift => "two" ※先頭のtwoを削除
5
s.unshift => ["three"] ※引数が無いので、何もしてない
6
s.push "four" => ["three", "four"]
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p s =>["three", "four"]

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a = [:a,:a,:b,:c]
2
a[5] = :e
3
a.concat([:a,:b,:c])
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a.compact
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a.uniq
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p a
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=> [:a, :a, :b, :c, nil, :e, :a, :b, :c]

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arr = [1, 2, 5, 5, 1, 3, 1, 2, 4, 3]
2
p arr.uniq
3
[1, 2, 5, 3, 4]

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a = [1, 2, 3, 4, 5, 6]
2

3
a.collect {|v| v * 2}
4
=> [2, 4, 6, 8, 10, 12]
5
a.inject {|v| v * 2}
6
=> 32
7
a.each {|v| v * 2}
8
=> [1, 2, 3, 4, 5, 6]
9
a.map {|v| v * 2}
10
=>[2, 4, 6, 8, 10, 12]
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a.select {|v| v * 2}
12
=> [1, 2, 3, 4, 5, 6]
13
a.execute {|v| v * 2}
14
=> error undefined method

1
sarray = %w(Apple Orange Grape)
2
sarray.each {|v| print v, " "}
3
#
4
Apple Orange Grape

1
s = <<EOB
2
Hello, Ruby World.
3
Hi, Ruby World.
4
Goodbye, Ruby World.
5
  EOB
6

7
#解答
8
5行目のEOBの前の空白を削除する。

1
puts "hello".encoding.name
2
UTF-8
3
=> nil

1
puts "0123456789-".delete("^13-56-")
2
=> 13456-

1
p "HogeHOGEhoge"[/[A-Z][^A-Z]+/]
2
=> "Hoge"

1
h = {1 => "Hoge", 2=> "Piyo", 3=>"fuga"}
2
p h.invert
3
#
4
{“Hoge”=>1, “Piyo”=>2,“fuga”=>3 }

1
a = {"Foo" => "Hoge", "Bar" => "Piyo", "Baz" => "Fuga"}
2
b = {"Foo" => "hoge", "Bar" => "piyo", "Baz" => "fuga"}
3
p a.update(b).sort{ |a, b| a[1] <=> b[1] }
4

5
[["Baz", "fuga"], ["Foo", "hoge"], ["Bar", "piyo"]]

1
open("test.txt","##AAA##") do |f|
2
  data = f.read.chomp
3
  data.reverse!
4
  f.rewind
5
  f.write data
6
end
7
#選択肢
8
# a, w, r, a+, r+, w+

1
puts 65.chr => "A"
2
puts "a".ord => 97

1
require 'securerandom'
2
SecureRandom.urlsafe_base64