Rubyの基本文法。チートシート-2。真偽値・配列・ハッシュ・正規表現

<h3>代入演算子</h3>

<table>
<tr><th>値</th><th>説明</td></tr>
<tr><td>a = b</td><td>aにbを代入する</td></tr>
<tr><td>a += b</td><td>a = a + b</td></tr>
<tr><td>a *= b</td><td>a = a * b</td></tr>
<tr><td>a /= b</td><td>a = a / b</td></tr>
<tr><td>a %= b</td><td>a = a % b</td></tr>
<tr><td>a |= b</td><td>a = a | b</td></tr>
</table>


<h2>配列</h2>

<h3>宣言</h3>

```ruby
hoge = [ 1, 2, 3 ]
 => [1, 2, 3]

Array.new(10)
 => [nil, nil, nil, nil, nil, nil, nil, nil, nil, nil]

hoge = Array.new( 5, 'hoge')
 => ["hoge", "hoge", "hoge", "hoge", "hoge"]

hoge = %w(apple banana carrot)
 => ["apple", "banana", "carrot"]

 hoge << 1
 => [1]
hoge << 2
 => [1, 2]
hoge << 3
 => [1, 2, 3]

 hoge[0]
 => 1
hoge.first
 => 1
hoge[1]
 => 2
hoge[2]
 => 3

[1, 2, 3] + [4, 5, 6]
 => [1, 2, 3, 4, 5, 6]

<h5>乗算</h5>

```ruby
[1, 2, 3] * 3 #各要素を3回分繰り返す
 => [1, 2, 3, 1, 2, 3, 1, 2, 3]

[1, 2, 3] * ',' # カンマ区切りの文字列
 => "1,2,3"

 hoge = { fuga: 'a', bar: 'b' }
 => {:fuga=>"a", :bar=>"b"}

Hash.new
 => {}

hoge = Hash.new(0) # キーが存在しない場合の値を指定できる
 => {}
hoge['a'] = 1
 => 1
hoge['a']
 => 1
hoge['b']
 => 0