Merge pull request #1226 from bobahop/patch-3

[char] about.md

Author: coriolinus

concepts/char/about.md

@@ -1,3 +1,42 @@
 # About
 
-TODO
+Rust implements the [char][char type] type to represent a single character. A `char` literal is placed within single quotes, like `'a'`.
+Each `char` is four bytes in size and represents a single [Unicode Scalar Value][unicode scalar].
+
+However, a [`char`][character type] is not always what we think of as a letter. There are some languages, e.g. Hindi,  that use [diacritics][diacritics],
+which are special symbols which modify the character they are attached to. Although the diacritic in Rust is a separate `char`, it is the diacritic and
+the character it modifies that we commonly think of as a letter.
+
+The term for a character and its diacritic is [grapheme cluster][grapheme cluster]. There are external crates that can be used to process grapheme clusters,
+such as [unicode-segmentation][unicode-segmentation].
+
+Example
+
+```rust
+pub fn main() {
+    let text = "ü"; // a "u" with a diacritic
+    let text_vec: Vec<char> = text.chars().collect(); // this gets the chars in "ü"
+    println!("{:?}", text_vec.len()); // this prints the number of chars in "ü"
+    println!("{:?}", text_vec[0]); // this prints the first char in "ü"
+    println!("{:?}", text_vec[1]); // this prints the second char in "ü"
+}
+```
+
+prints
+
+```rust
+2
+'u'
+'\u{308}'
+```
+
+'\u{308}' is another way of writing a `char` literal. `\u` indicates it is a unicode `char` with `{308}` being the unique Unicode number for that character
+or diacritic.
+
+[char type]: https://doc.rust-lang.org/std/primitive.char.html
+[unicode]: http://www.unicode.org/glossary/#unicode
+[character type]: https://doc.rust-lang.org/book/ch03-02-data-types.html#the-character-type
+[unicode scalar]: http://www.unicode.org/glossary/#unicode_scalar_value
+[diacritics]: http://www.unicode.org/glossary/#diacritic
+[grapheme cluster]: https://doc.rust-lang.org/book/ch08-02-strings.html#bytes-and-scalar-values-and-grapheme-clusters-oh-my
+[unicode-segmentation]: https://crates.io/crates/unicode-segmentation