puts "なかじ".encoding.name #=>UTF-8

p "B".ord #=> 66

p 66.chr #=>"B"

a = {"Yasai" => "nasu", "Kudamono"=>"ichigo", "Sakana"=>"katsuo"}
p a.sort{|a,b|a[1]<=> b[1]} #=>[["Kudamono", "ichigo"], ["Sakana", "katsuo"], ["Yasai", "nasu"]]

a = {"Yasai" => "nasu", "Kudamono"=>"ichigo", "Sakana"=>"katsuo"}
p a.sort{|a,b|a[1]<=> b[1]}.to_h #=>{"Kudamono"=>"ichigo", "Sakana"=>"katsuo", "Yasai"=>"nasu"}

File.open("nyan_by_w.txt","??") do |f|
    data = f.read.chomp 
    data.reverse!
    f.rewind
    f.write data
end

Wanko is a friend

dneirf a si oknaW

Wanko is a frienddneirf a si oknaW

p File.join("ruby", "exam","silver")#=>"ruby/exam/silver"

p [1,2,3].zip #=>[[1], [2], [3]]

a = ["a", "b", "c"]
b = [1,2,3]
a.zip(b){|x| p [x]} 
#=>["a", 1]
#=>["b", 2]
#=>["c", 3]

a = ["a", "b", "c"]
b = [1,2,3]
a.zip(b).each{|x| p [x]} 

a = ["a", "b", "c"]
b = [1,2,3]
a.zip(b){|x, y| p [x,y]} 

a = ["a", "b", "c"]
b = [1,2,3]
a.zip(b).each{|x, y| p [x,y]} 

a = ["a", "b", "c", "d"]
b = [1,2,3,4]
p [a,b]
[a,b].zip{|x,y| p [x,y]}
#=>[["a", "b", "c", "d"], [1, 2, 3, 4]]
#=>["a", "b"]
#=>[1, 2]

a = ["a", "b", "c", "d"]
b = [1,2,3,4]
p [a,b]
[a,b].zip.each{|x,y| p [x,y]}
#=>[["a", "b", "c", "d"], [1, 2, 3, 4]]
#=>[["a", "b", "c", "d"], nil]
#=>[[1, 2, 3, 4], nil]

a = ["a", "b", "c"]
b = [1,2,3]
p [a,b].transpose #=>[["a", 1], ["b", 2], ["c", 3]]
[a,b].transpose.each{|x, y| p [x,y]}
#=>["a", 1]
#=>["b", 2]
#=>["c", 3]

a = ["a", "b", "c"]
b = [1,2,3]
p [a,b].transpose #=>[["a", 1], ["b", 2], ["c", 3]]
[a,b].transpose.each{|x| p x}
#=>["a", 1]
#=>["b", 2]
#=>["c", 3]

a = ["a", "b", "c"]
b = [1,2,3]
p [a,b].transpose #=>[["a", 1], ["b", 2], ["c", 3]]
[a,b].transpose.each{|x| p [x]}
#=>[["a", 1]]
#=>[["b", 2]]
#=>[["c", 3]]

p [1, 2, 3].inject{|x, y| x + y ** 2} rescue p $! #=>14
p [1, 2, 3].inject do|x, y| x + y ** 2 end rescue p $! #=>#<ArgumentError: wrong number of arguments (given 0, expected 1..2)>

p [1, 2, 3].inject(0){|x, y| x + y ** 2} rescue p $! #=>最初に渡すのは初期値0と1で結果は14

p [1, 2, 3].inject{|x, y| x + y ** 2} rescue p $! #=>最初に渡すのは初期値1と2で結果は14
 p [1].inject{|x, y| x + y ** 2} rescue p $! #=>1（エラーにはなりません）

p [1, 2, 3, 4, 5].inject(:+) #=>15

p [1, 2, 3, 4, 5].inject(:*) #=>120

p [1, 2, 3, 4, 5].inject(:-) #=>-13

numbers = [3,89,40,39,29,10,50,59,69]
num = numbers.inject do |i,j|
  i > j ? i : j #=>大きい方の値が残る
end
p num #=>89

p ([1, 2, 3].inject) do|x, y| x + y ** 2 end rescue p $! #=>#<ArgumentError: wrong number of arguments (given 0, expected 1..2)>

p [1, 2, 3].inject(0) do|x, y| x + y ** 2 end rescue p $! #=>#<TypeError: 0 is not a symbol nor a string>

p (1..5).each_cons(3){|v| p v }
#=>[1, 2, 3]
#=>[2, 3, 4]
#=>[3, 4, 5]
#=>1...5 今回関係ないけどpメソッドが()の引数のみ出力しているのがわかる例だなと思って

p (1..2).each_cons(3){|v| p v } #=>何も出力されない

(1..7).each_slice(3){|v| p v }
#=>[1, 2, 3]
#=>[4, 5, 6]
#=>[7]

(1..2).each_slice(3){|v| p v } #=>[1, 2]

# 読み込み用
  def foo
    @@foo
  end
# 書き込み用
  def foo=(value) 
    @@foo = value
  end

class Foo
  @@foo = 'grass🌱'

  def foo
    @@foo
  end

  def foo=(value) 
    @@foo = value
  end
end
foo1 = Foo.new
foo1.foo = 'goat🐐'
foo2 = Foo.new
foo2.foo  = 'lion🦁'
puts foo1.foo #=>lion🦁
puts foo2.foo #=>lion🦁

class Foo
  @@var = 'grass🌱'

  def var
    @@var
  end

  def var=(value)
    @@var = value
  end
end

class Bar < Foo
end

foo = Foo.new
foo.var = 'goat🐐'
bar = Bar.new
bar.var = 'lion🦁'
p foo.var #=>lion🦁
p bar.var #=>lion🦁

class Foo
  @foo = 'grass🌱'

  def foo #attr_reader :fooに書き換えOK
    @foo
  end

  def foo=(value) #attr_writer :fooに書き換えOK
    @foo = value
  end
# 上記二つまとめてattr_accessor :foo にできます
end
foo1 = Foo.new
foo1.foo = 'goat🐐' 
foo2 = Foo.new
foo2.foo  = 'lion🦁'
puts foo1.foo#=>goat🐐
puts foo2.foo #=>lion🦁

a1 = "abc"
a2 = 'abc'

print a1.equal? a2
print a1.eql? a2
#=>falsetrue

h = Hash.new([]) 
p h[:a] #=>[]

h = Hash.new([])
h.default = nil
p h.default #=> nil
p h[:a] #=>nil

h = Hash.new("default value")
h[:a]
h[:b] = 100
p h[:a] #=>"default value"
p h #=>{:b=>100}

hash = Hash.new {|h, k| raise(KeyError, "Key #{k} does not exist in hash #{h}") }
hash.default_proc = nil
p hash[:a] #=>nil

$val = 0

class Count
  def self.up
    $val = $val + 1
    $val == 3 ? true : false
  end
end

[*1..10].any? do
  Count.up
end

p $val #=> 3

$val = 0

class Count
  def self.up
    $val = $val + 1
    $val == 100 ? true : false
  end
end

[*1..10].any? do
  Count.up
end

p $val #=> 10

p %(a b c)  # => "a b c"
p %(とま  と ま) #=>"とま  と ま"

p %s(a)     # => :a
p %s(a b)  #=>:"a b"

p %w(a b c) # => ["a", "b", "c"]
p %W(a b c) # => ["a", "b", "c"]
p %W(a b  c) # => ["a", "b", "c"]
%w(foo\ bar baz)=> ["foo bar", "baz"]

h = Hash.new("default value")
h[:some] = "some"
p h #=> {:some=>"some"}

h.clear

p h #=> {}
p h.default #=> "default value"

a = [1, 2, 3]
a.each_index { |n| puts n }
#=>0
#=>1
#=>2

a = [1, 2, 3]
a.each_index { |n, index| puts n, index }
#=>0
#=>
#=>1
#=>
#=>2
#=>

a = [1, 2, 3]
a.each_with_index { |n, index| puts n,index }
#=>0
#=>1
#=>1
#=>2
#=>2
#=>3

Thread.new {}   # => #<Thread:0x00007fc5e0836000@(irb):1 run>
Thread.start {} # => #<Thread:0x00007ffaa68110e8@(irb):2 run>
Thread.fork {}  # => #<Thread:0x00007f917003cb28@(irb):3 run>

s = <<EOF
    Hello,
    Nakaji
    EOF
p s #=>sj37.rb:1: can't find string "EOF" anywhere before EOF (SyntaxError)

s = <<EOF
    Hello,
    Nakaji
EOF
p s #=>"    Hello,\n    Nakaji\n"

s = <<-EOF
    Hello,
    Nakaji
    EOF
p s #=>"    Hello,\n    Nakaji\n"

s = <<~EOF
    Hello,
    Nakaji
    EOF
p s #=>"Hello,\nNakaji\n"

s = <<'EOB'
Hello.\nRuby
World.
EOB
puts s
#=>Hello.\nRuby
#=>World.
p s #=>"Hello.\\nRuby\nWorld.\n"

s = <<"EOB"
Hello.\nRuby
World.
EOB
puts s
#=>Hello.
#=>Ruby
#=>World.
p s #=>"Hello.\nRuby\nWorld.\n"

klass = Class.new
hash = {klass => 100}
puts hash[klass] #=>100
# 参考
puts hash #=>{#<Class:0x00000001028356f0>=>100}

klass = Class.new
hash = {klass: 100}
puts hash[klass] #=>
# 参考
puts hash[:klass]  #=>100
puts hash #=>{:klass=>100}

klass = Class.new
hash = {}
hash.store(klass, 100)
puts hash[klass] #=>100

klass = Class.new
hash = {}
hash.store(:klass, 100)
puts hash[klass] #=>
# 参考
puts hash[:klass] #=>100
puts hash #=>{:klass=>100}

klass = Class.new
hash = Hash[klass, 100]
puts hash[klass]
# 参考
puts hash #=>{#<Class:0x0000000102db5c88>=>100}

array = [1, 2, 3]
p array.push 4 #=>[1, 2, 3, 4]
p array.push [5, 6] #=>[1, 2, 3, 4, [5, 6]]
p array.push 7, 8 #=>[1, 2, 3, 4, [5, 6], 7, 8]
p array.push #=>[1, 2, 3, 4, [5, 6], 7, 8]
p array #=>[1, 2, 3, 4, [5, 6], 7, 8]

array = [1, 2, 3]
p array.pop(3)   #=> [1,2, 3]
p array.pop #=>nil
p array.pop(1) #=>[]
p array #=>[]

arr = [1,2,3]
arr.unshift 0
p arr             #=> [0, 1, 2, 3]
arr.unshift [0]
p arr             #=> [[0], 0, 1, 2, 3]
arr.unshift 1, 2
p arr             #=> [1, 2, [0], 0, 1, 2, 3]

a = [0, 1, 2, 3, 4]
p a.shift            #=> 0
p a                  #=> [1, 2, 3, 4]
p [].shift           #=> nil
p [].shift(1)        #=> []

-12345.abs   # => 12345
12345.abs    # => 12345
-1234567890987654321.abs   # => 1234567890987654321

2.abs2    # => 4
-2.abs2   # => 4
2.0.abs2  # => 4
-2.0.abs2 # => 4

1.next      #=> 2
(-1).next   #=> 0
1.succ      #=> 2
(-1).succ   #=> 0

p "Apple-Banana-Lemon".split /-/ #=>["Apple", "Banana", "Lemon"]

p "Apple-Banana-Lemon".split /(-)/ #=>["Apple", "-", "Banana", "-", "Lemon"]

puts 0b2 #=>numeric literal without digits (SyntaxError)

arr = [
  "a".to_i(36), #=>36進数でのa
  "070".to_i(0), # =>8進数での70=56
  nil.to_i, # = > 0
  "0b0001".to_i #=> 0(引数0か2を入れれば1になる）
]

p arr

p "1f".to_i(16)   # => 31
p "0x1f".to_i(16) # => 31
p  "0x1f".to_i(0) # => 31
p  "1f".to_i(0) # => 1

p  "nil".to_i #=>0

p  "true".to_i #=>undefined method `to_i' for false (NoMethodError)
p  "false".to_i #=>undefined method `to_i' for false (NoMethodError)

puts '10'.oct #=>8
puts 'A'.oct #=>8
puts '0b10'.oct=>2
puts '9'.oct=>0

p "byz".hex #=>11
p "xyz".hex #=>0

def foo(n)
  n ** n
end

puts foo(2) * 2 #=>8

def foo(n)
  n ** n
end

puts foo (2) * 2 #=>256

arr = Array(3){"a"}
arr.first.upcase!
p arr #=> undefined method `upcase!' for an instance of Integer (NoMethodError)

arr = Array(3){"a"}
p arr #=>[3]
p arr.first #=>3

MAX = 10
print MAX
MAX = 100
print MAX
#=>10
#=>sj11.rb:3: warning: already initialized constant MAX
#=>sj11.rb:1: warning: previous definition of MAX was here
#=>100

MAX = 'tomato'
p MAX #=>"tomato"
p MAX.upcase! #=>"TOMATO"
p MAX #=>"TOMATO"

MAX = 'tomato'
p MAX.object_id #=>60
p MAX.upcase! #=>"TOMATO"
p MAX.object_id  #=>60

def hoge
  x = 10
  Y = x < 10 ? "C" : "D"
  puts Y
end
hoge #=>dynamic constant assignment (SyntaxError)

a, b = 0    # , b => nil
p a  #=> 0
p b  #=> nil

a = 1, 2 #=> [1, 2]
a #=> [1, 2]

a, b = 1, 2, 3 #=> [1, 2, 3]
a #=> 1
b #=> 2

a, *b = 1, 2, 3 #=> [1, 2, 3]
a #=> 1
b #=> [2,3]

v1 = 1 - 1 == 0
v2 = v1 || raise RuntimeError #ここでv1 || raiseを評価してしまい、syntax error, unexpected constant, expecting `do' or '{' or '(' (SyntaxError)　となる
puts v2 && false

v2 = v1 or raise RuntimeError

v2 = v1 || raise(RuntimeError)

v2 = v1 || (raise RuntimeError)

p "foo" * 2 **2 #=>"foofoofoofoo"

a, = (1..5).partition(&:odd?)
p a #=>[1, 3, 5]

a,b = (1..5).partition(&:odd?)
p a #=>[1, 3, 5]
p b #=>[2,4]

a = (1..5).partition(&:odd?)
p a #=>[[1, 3, 5], [2, 4]]

odd_numbers, _even_numbers = [*1..5].partition { |num| :odd?.to_proc.call(num) }
p odd_numbers #=>[1,3,5]

p [1,2,3,4,5].partition(!&:even?) #=> syntax error, unexpected & (SyntaxError)

[1, 1, 4, 2, 3] | [5, 4, 5]  #=> [1, 4, 2, 3, 5]

a = [1, 2, 5, 7, 8]
b = [1, 3, 6, 7, 9]
c =  nil || a & b | a && a | b
p c

s = "To be or not to be, that is the question."
hash = Hash.new(0)
s.scan(/\w+/) {|i| hash[i] += 1}
p hash["be"] #=>2

s = "To be or not to be, that is the question."
hash = Hash.new(0)
p s.scan(/\w+/) #=>["To", "be", "or", "not", "to", "be", "that", "is", "the", "question"]

s = "To be or not to be, that is the question."
hash = Hash.new(0)
p hash #=>{}
p s.scan(/\w+/){|i| hash[i] += 1}
p hash #=>{"To"=>1, "be"=>2, "or"=>1, "not"=>1, "to"=>1, "that"=>1, "is"=>1, "the"=>1, "question"=>1}
p hash["be"]#=>2

s = "To be or not to be, that is the question."
hash = Hash.new(0)
p s.match(/\w+/)#=>#<MatchData "To">
s.match(/\w+/) {|i| hash[i] += 1}
p hash #=>{#<MatchData "To">=>1}

s = "To be or not to be, that is the question."
hash = Hash.new(0)
s.sub(/\w+/) {|i| hash[i] += 1}
p hash #=>{"To"=>1}

foo = [1,2,3]
bar = foo
baz = foo.dup

bar[3] = 4
p foo.object_id #=>60
p bar.object_id #=>60
p baz.object_id #=>80
p foo #=>[1, 2, 3, 4]
p bar #=>[1, 2, 3, 4]
p baz #=>[1, 2, 3]

str = "100,200,300,400,500"
p str.split(",") #=>["100", "200", "300", "400", "500"]
p str #=>"100,200,300,400,500"

str = "a,b,c,d"
p str.split(/,/, 2) #=>["a", "b,c,d"]
p str.split(/,/, 3) #=>["a", "b", "c,d"]

ary = ["100", "200", "300", "400", "500"]
p ary.join("\n") #=>"100\n200\n300\n400\n500"
p ary #=> ["100", "200", "300", "400", "500"]

p String.instance_methods.grep(/strip/)
#=>[:strip, :lstrip, :rstrip, :strip!, :lstrip!, :rstrip!]

class NonasciiError < StandardError
end

File.open("sample.txt") do |io|
  io.each_line do |str|
    begin
      raise(NonasciiError, "non ascii character detected") unless str.ascii_only?
    rescue => ex
      puts "#{ex.message} : #{str}"
    end
  end
end
#=>non ascii character detected : ルビーアソシエーション
#=>non ascii character detected : るび

Ruby Association
ルビーアソシエーション
るびー
Ruby on Rails

puts "Ruby on Rails".delete("Railso") #=>uby n
puts "Ruby on Rails".delete("^Rail")#=>RRail

/^[hc].*o$/i
#=>Hello,Cello

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

s = "Hello"
def s.greet
    puts "Hi!"
end
class String
    def greet
        puts "Hello"
    end
end


s.greet.class #=>Hi!
p s.singleton_class.method_defined?(:greet)#=>true
p s.class.method_defined?(:greet)"=>true

p ?A #=>"A"

p ?あ #=>"あ"
puts ?あ #=>あ

p ?あい #=>syntax error, unexpected local variable or method, expecting end-of-input (SyntaxError)

exceptions = {
  NameError => "変数または定数が存在しません",
  ArgumentError => "引数が不正です",
  RuntimeError => "特定の例外が発生しました"
}

begin
  raise
rescue => e
  puts exceptions[e.class] #=>特定の例外が発生しました
else
  puts "例外は発生しませんでした"
end