From cb941420422df384ace4e88a2dfc6346879efb19 Mon Sep 17 00:00:00 2001
From: jbranchaud <jbranchaud@gmail.com>
Date: Mon, 21 Jul 2025 17:38:41 -0500
Subject: [PATCH] Add Decompose Unicode Character With Diacritic Mark as a Ruby
 TIL

---
 README.md                                     |  3 +-
 ...e-unicode-character-with-diacritic-mark.md | 55 +++++++++++++++++++
 2 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 ruby/decompose-unicode-character-with-diacritic-mark.md

diff --git a/README.md b/README.md
index 65e00fb..673c909 100644
--- a/README.md
+++ b/README.md
@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
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+_1653 TILs and counting..._
 
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@@ -1314,6 +1314,7 @@ If you've learned something here, support my efforts writing daily TILs by
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+- [Decompose Unicode Character With Diacritic Mark](ruby/decompose-unicode-character-with-diacritic-mark.md)
 - [Defaulting To Frozen String Literals](ruby/defaulting-to-frozen-string-literals.md)
 - [Define A Custom RSpec Matcher](ruby/define-a-custom-rspec-matcher.md)
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diff --git a/ruby/decompose-unicode-character-with-diacritic-mark.md b/ruby/decompose-unicode-character-with-diacritic-mark.md
new file mode 100644
index 0000000..d040697
--- /dev/null
+++ b/ruby/decompose-unicode-character-with-diacritic-mark.md
@@ -0,0 +1,55 @@
+# Decompose Unicode Character With Diacritic Mark
+
+A character like the `ñ` is typically represented by the unicode codepoint of
+`U+00F1`. However, it is also possible to represent it with two unicode
+codepoints -- the `n` (`U+006E`) and the combining diacritical mark `˜`
+(`U+0303`).
+
+We can see that by comparing a typed `ñ` with one where we split it apart into
+the separate codepoints. We can do that with
+[`#unicode_normalize`](https://apidock.com/ruby/v2_5_5/String/unicode_normalize)
+and the `:nfd` argument which stands for _Normalized Form Decomposed_.
+
+```ruby
+> "ñ" == "ñ".unicode_normalize(:nfd)
+=> false
+> "ñ".unicode_normalize(:nfd).length
+=> 2
+> "ñ".length
+=> 1
+```
+
+We can inspect the exact codepoints by iterating over each character and
+printing out the codepoint value.
+
+```ruby
+"ñ".each_char.with_index do |char, i|
+  puts "#{i}: '#{char}' -> U+#{char.ord.to_s(16).upcase.rjust(4, '0')}"
+end
+# 0: 'ñ' -> U+00F1
+# => "ñ"
+
+"ñ".unicode_normalize(:nfd).each_char.with_index do |char, i|
+  puts "#{i}: '#{char}' -> U+#{char.ord.to_s(16).upcase.rjust(4, '0')}"
+end
+# 0: 'n' -> U+006E
+# 1: '̃' -> U+0303
+#=> "ñ"
+```
+
+Notice the difference after the character has been decomposed such that the
+diacritic is separated from the character.
+
+This can be done with other characters containing diacritics.
+
+And here we go the other direction with
+[`#pack`](https://ruby-doc.org/core-3.0.1/Array.html#method-i-pack).
+
+```ruby
+> [0x006E, 0x0303].pack("U*")
+=> "ñ"
+> [0x00F1].pack("U*")
+=> "ñ"
+> [0x006E, 0x0303].pack("U*") == [0x00F1].pack("U*")
+=> false
+```