Day 2 ~ 13： Ruby 認定試験による勉強

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

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

MAX=10
print MAX
MAX=100
print MAX

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

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

#引数baseを取ることもでき、その引数で何進数かを示す。
#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。
変数.to_i(2)

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

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

# 選択肢
1: a[0..3], 2: a[0..-2], 3: a[0...-2], 4: a[0...-3],
5: a[3,0], 6: a[0,3], 7: a[2,0], 8: a[0,2]
# 答えは2と6

money = 1000
オブジェクト.upto(max) do |i|
  実行処理
end

money = 100
1.upto(3) do |i|
  money = money * 1.1
end
puts money.to_i

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

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

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

class User
  attr_accessor:say
  def initialize
    @say = "Hello"
  end
end
class Oriver < User
  def initialize
    super
  end
end

oriver = User.new
puts oriver.say
#実行結果：Hello
#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

#円の面積
include Math
def area r
  return r * r * PI
end

#球の体積
def volume r
  return (4/3) * r * r * r * PI
end

#πの値
puts PI #結果：3.141592653589793
area(2) #結果：12.566370614359172
volume (2)  : 25.132741228718345

| ^ & <=> == === =~ > >= < <= << >>
+ - * / % ** ~ +@ -@ [] []= ` ! != !~

= ?: .. ... not && and || or ::

# 二項演算子
def +(other) # obj + other
def -(other) # obj - other

# 単項プラス/マイナス
def +@ # +obj
def -@ # -obj

# 要素代入
def foo=(value) # obj.foo = value

# [] と []=
def [](key) # obj[key]
def []=(key, value) # obj[key] = value
def []=(key, key2, value) # obj[key, key2] = value

# バッククォート記法
def `(arg) # `arg` または %x(arg)

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

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

  def to_s
    return "#{@id}:#{@name}"
  end
#ここに代入する式を選択して下さい。
end

employees = []
employees << Employee.new("3","Tanaka")
employees << Employee.new("1","Suzuki")
employees << Employee.new("2","Sato")
employees.sort!
employees.each do |employee| puts employee end

# 実行結果
1:Suzuki
2:Sato
3:Tanaka

# 選択肢
# 1 (答え）
def <=> other
  return self.id <=> other.id
end

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

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

# 問題選択肢
1. find_allとselectは同じ動作をする。
2. mapとcollectは同じ動作をする。
3. findとselectは同じ動作をする。
4. firstは先頭要素を削除し、その要素を返す。
5. concatは非破壊的メソッドである。
6. concat!は破壊的メソッドである。

#解答
1と2

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

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

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

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

a1=%w(a b)
a2=%w(x y)
a3=a1.zip(a2)
p a3.first

# 選択肢
1: "a", 2: ["a"], 3: ["a", "x"], 4: ["a", "b"], 5. 例外が発生する。
# 解答

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

a = ["a", "b", "c"]
b = [1, 2, 3]
##AAA##

#実行結果
["a", 1]
["b", 2]
["c", 3]

#選択肢
a.zip(b).each{|x| p x }
a.zip(b){|x| p x }
[a, b].zip{|x, y| p [x, y] }
[a, b].transpose.each{|x, y| p [x, y] }

#答え 1，2，4

a = [1,2,3,4,5]
p a.slice(1,3)

#答え

a = "abc"
b = "abc"
print a.eql? b
print a.equal? b
print a == b

# =>
# true false true

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

# => ?

# irb
s1 = "Hoge"
s2 = "Fuga"

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

s = "123456789"
p s[1,4]

# =>
# "2345"

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

#答え %

#{} の問題
v = {}
v.class
#出力答え Hash

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

#配列、シンボル 問題
h = #ここに代入する式を選択して下さい。
p h
#選択肢
1: {a:1,b:2,c:3}, 2: {a=1,b=2,c=3}
3. Hash[:a, 1, :b, 2, :c, 3], 4: {:a1,:b2,:c3}
#実行結果
{ :a => 1, :b => 2, :c => 3 }

#答え ４

sprintf("%d", 4);
=> "4"

# %2d 2桁の文字列を返す
sprintf("%2d", 4);
=> " 4"

# %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。
sprintf("%02d", 4);
=> "04"

# ファイルdataの内容はabcdefg

File.open("data") do |io|
  while not io.eof?
    print io.read(1)
    io.seek(0,IO::SEEK_SET)
  end
end

#答え: aが表示され続ける

# 問題
t = Time.gm(1970,1,1)
puts t.strftime("#ここに代入する式を選択")
# => 1970/01/01

#選択肢
1, %y/%m/%d ,2, %Y/%M/%d
3, %y/%M/%d ,4, %Y/%m/%d

#答え：4

# 問題
while rand
goto class const

#答え whileとclass

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

#解答 1 2 3 0
# 1，2，3は表示上は数字型だか、実は文字型

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

# =>
# x = 0

[1,2,3].each do |x|
  print x.to_s + " "
  print x.to_s.class
  o_s.class
end
puts x

# 0
# => nil

#問題
nil 0 "" false 0.0 NULL

#解答 nil と false

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

#答え &&

# 問題
HOGE = "hoge"
HOGE.gsub!("hoge", "piyo")
print HOGE

# 答え  警告は発生せず、「piyo」が表示される。

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

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

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

# 問題
p ?A

#答え "A"

#コード１
p "A".ord
# => 65

#コード２
p 65.chr
#=> "A"

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

# A １のみ

Kernel.call
=>Module

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

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

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

a=[1,2,3,4]

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

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

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

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

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

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

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

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

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

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

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

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

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

s = <<EOB
Hello, Ruby World.
Hi, Ruby World.
Goodbye, Ruby World.
  EOB

#解答
5行目のEOBの前の空白を削除する。

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

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

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

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

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

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

open("test.txt","##AAA##") do |f|
  data = f.read.chomp
  data.reverse!
  f.rewind
  f.write data
end
#選択肢
# a, w, r, a+, r+, w+

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

require 'securerandom'
SecureRandom.urlsafe_base64