Merge pull request #947 from jansol/master

Add subchapter about (byte)string literals

Author: steveklabnik

src/std/str.md

@@ -57,5 +57,110 @@ More `str`/`String` methods can be found under the
 [std::string][string]
 modules
 
+## Literals and escapes
+
+There are multiple ways to write string literals with special characters in them.
+All result in a similar `&str` so it's best to use the form that is the most
+convenient to write. Similarly there are multiple ways to write byte string literals,
+which all result in `&[u8; N]`.
+
+Generally special characters are escaped with a backslash character: `\`.
+This way you can add any character to your string, even unprintable ones
+and ones that you don't know how to type. If you want a literal backslash,
+escape it with another one: `\\`
+
+String or character literal delimiters occuring within a literal must be escaped: `"\""`, `'\''`.
+
+```rust,editable
+fn main() {
+    // You can use escapes to write bytes by their hexadecimal values...
+    let byte_escape = "I'm writing \x52\x75\x73\x74!";
+    println!("What are you doing\x3F (\\x3F means ?) {}", byte_escape);
+
+    // ...or Unicode code points.
+    let unicode_codepoint = "\u{211D}";
+    let character_name = "\"DOUBLE-STRUCK CAPITAL R\"";
+
+    println!("Unicode character {} (U+211D) is called {}",
+                unicode_codepoint, character_name );
+
+
+    let long_string = "String literals
+                        can span multiple lines.
+                        The linebreak and indentation here ->\
+                        <- can be escaped too!";
+    println!("{}", long_string);
+}
+```
+
+Sometimes there are just too many characters that need to be escaped or it's just
+much more convenient to write a string out as-is. This is where raw string literals come into play.
+
+```rust, editable
+fn main() {
+    let raw_str = r"Escapes don't work here: \x3F \u{211D}";
+    println!("{}", raw_str);
+
+    // If you need quotes in a raw string, add a pair of #s
+    let quotes = r#"And then I said: "There is no escape!""#;
+    println!("{}", quotes);
+
+    // If you need "# in your string, just use more #s in the delimiter.
+    // There is no limit for the number of #s you can use.
+    let longer_delimiter = r###"A string with "# in it. And even "##!"###;
+    println!("{}", longer_delimiter);
+}
+```
+
+Want a string that's not UTF-8? (Remember, `str` and `String` must be valid UTF-8)
+Or maybe you want an array of bytes that's mostly text? Byte strings to the rescue!
+
+```rust, editable
+use std::str;
+
+fn main() {
+    // Note that this is not actually a &str
+    let bytestring: &[u8; 20] = b"this is a bytestring";
+
+    // Byte arrays don't have Display so printing them is a bit limited
+    println!("A bytestring: {:?}", bytestring);
+
+    // Bytestrings can have byte escapes...
+    let escaped = b"\x52\x75\x73\x74 as bytes";
+    // ...but no unicode escapes
+    // let escaped = b"\u{211D} is not allowed";
+    println!("Some escaped bytes: {:?}", escaped);
+
+
+    // Raw bytestrings work just like raw strings
+    let raw_bytestring = br"\u{211D} is not escaped here";
+    println!("{:?}", raw_bytestring);
+
+    // Converting a byte array to str can fail
+    if let Ok(my_str) = str::from_utf8(raw_bytestring) {
+        println!("And the same as text: '{}'", my_str);
+    }
+
+    let quotes = br#"You can also use "fancier" formatting, \
+                    like with normal raw strings"#;
+
+    // Bytestrings don't have to be UTF-8
+    let shift_jis = b"\x82\xe6\x82\xa8\x82\xb1\x82"; // "ようこそ" in SHIFT-JIS
+
+    // But then they can't always be converted to str
+    match str::from_utf8(shift_jis) {
+        Ok(my_str) => println!("Conversion successful: '{}'", my_str),
+        Err(e) => println!("Conversion failed: {:?}", e),
+    };
+}
+```
+
+For conversions between character encodings check out the [enconding][encoding-crate] crate.
+
+A more detailed listing of the ways to write string literals and escape characters
+is given in the ['Tokens' chapter][tokens] of the Rust Reference.
+
 [str]: https://doc.rust-lang.org/std/str/
 [string]: https://doc.rust-lang.org/std/string/
+[tokens]: https://doc.rust-lang.org/reference/tokens.html
+[encoding-crate]: https://crates.io/crates/encoding