Update ruby and pacman notes

notes/language/ruby/array.md

@@ -9,6 +9,7 @@ ref: https://docs.ruby-lang.org/en/3.4/Array.html
 my_array = Array.new
 my_array = [1, 2, 3]
 my_array = (1..10).to_a
+my_words = %w[foo bar]  # %W if going to use string interpolation
 
 my_array[1]
 my_array.push(40)
@@ -23,9 +24,11 @@ my_array << 40  # Same as push
 | `max`      | Returns the biggest element in the array.                         |
 | `min`      | Returns the smallest element in the array                         |
 | `include?` | Returns `true` if the array includes the specified element.       |
+| `empty?`   | Returns `true` if the length of the array is 0.                   |
 | `sort`     | Returns a new array sorted.                                       |
 | `sort_by!` | Sort in place by using the given block.                           |
 | `reverse`  | Returns a new array in inverse order.                             |
+| `each`     | Iterate over the elements of the array.                           |
 | `map`      | Returns a new array with each element updated by the given block. |
 | `collect`  | Same as `map`.                                                    |
 
@@ -35,6 +38,14 @@ Check if array includes an element:
 my_array.include? 'critical'
 ```
 
+Iterate array elements:
+
+```ruby
+array.each do |element|
+  puts element
+end
+```
+
 Update elements order:
 
 ```ruby

notes/language/ruby/builtin.md

@@ -2,9 +2,15 @@
 title: Built-in
 ---
 
-## Interactive Console
+## Usage
 
-Run the command:
+Usually it is expected to have the default tools and libraries.
+
+```shell
+pacman -S ruby-stdlib
+```
+
+Open the interactive console:
 
 ```shell
 irb
@@ -19,12 +25,6 @@ print 'Hello'  # Prints something and do NOT put a new line
 puts 'Hello'   # Prints something and puts a new line at the end
 ```
 
-[String formatting](https://docs.ruby-lang.org/en/3.4/format_specifications_rdoc.html):
-
-```ruby
-sprintf('%.1f', 8.199)
-```
-
 Getting user input:
 
 ```ruby

notes/language/ruby/hash.md

@@ -17,15 +17,15 @@ Create filled hash:
 ```ruby
 my_hash = {
   'name' => 'Taro',
-  'age' => 24,
+  'age' => 24
 }
 my_hash = {
   :name => 'Taro',
-  :age => 24,
+  :age => 24
 }
 my_hash = {
   name: 'Taro',  # Becomes symbol
-  age: 24,       # Becomes symbol
+  age: 24        # Becomes symbol
 }
 ```
 

notes/language/ruby/string.md

@@ -5,12 +5,28 @@ ref: https://docs.ruby-lang.org/en/3.4/String.html
 
 ## Basic
 
+To make strings immutable (recommended),
+add this the first line of the script:
+
+```ruby
+# frozen_string_literal: true
+```
+
+Instantiation:
+
 ```ruby
 my_string = 'Taro'
 interpolation = "Hello, #{name}"
 my_string << 'concatenate me'
 ```
 
+[String formatting](https://docs.ruby-lang.org/en/3.4/format_specifications_rdoc.html):
+
+```ruby
+format('%.1f', 8.199)  # Preferred
+sprintf('%.1f', 8.199)
+```
+
 ### Methods
 
 | Method       | Description                                        |

notes/tool/linux/arch/pacman.md

@@ -17,13 +17,20 @@ ref: https://wiki.archlinux.org/title/Pacman
 | `pacman -Qett` | List all packages explicitly installed and not required as dependencies (required only) |
 | `pacman -Qi package` | Check information of a package that is installed. |
 | `pacman -Si package` | Check information of a package that may not be installed. |
+| `pacman -D --asdeps` | Mark the specified package as installed as a dependency. |
 
 Check packages explicitly installed but required dependency at the same time.
 
 ```fish
 diff -y (pacman -Qqett | psub) (pacman -Qqe | psub)
 ```
 
+Mark a package as installed as a dependency.
+
+```fish
+sudo pacman -D --asdeps ruby
+```
+
 ## Configuration
 
 ### Parallel downloads