Add lang-question_mark.rs

Author: BlockBlazeDev

.travis.yml

@@ -1,5 +1,5 @@
 language: rust
-rust: 1.4.0
+rust: 1.13.0
 env:
 global:
 - secure: YuWDOwPGprL6PiBZVeGaLOCHHgC18fQ6nq617tlt7XFCkG17r/xDWq3iiAyNxNUcwsD9CkWi5aXok8SlX3rQx84XC/sya2bi0+8Frt9EztcVxgMwWuX3Ll4mFHO7HnMhazoQYRPd0b0w4s7bFY2WidxCqjsMKRgAM26Gn+6oQto=

README.md

@@ -7,7 +7,7 @@ rust-examples [![Open HUB statistics](https://www.openhub.net/p/rust-examples/wi
 gather example codes from tutorial and other documentations of
 [Rust](http://www.rust-lang.org/) into files, ready to compile.
 
-Examples are tested with version 1.3.0.
+Examples are tested with version 1.13.0.
 
 ## Files
 
@@ -39,6 +39,7 @@ Examples are tested with version 1.3.0.
     * Generics, Polymorphism, by [Felix S. Klock II](https://github.com/Rust-Meetup-Paris/Talks/tree/master/introduction_to_rust): `lang-generics.rs`
     * Overloading by [Rust By Example](http://rustbyexample.com/ops.html): `lang-overloading.rs`
     * Pointer snippets from Dave Herman's talk: `lang-pointers.rs`
+    * Question mark operator introduced in [Rust-1.13](https://blog.rust-lang.org/2016/11/10/Rust-1.13.html): `lang-question_mark.rs`
     * [std::collections:HashMap](https://doc.rust-lang.org/std/collections/struct.HashMap.html): `api-collections-hashmap.rs`
     * [getopts](http://doc.rust-lang.org/getopts/getopts/index.html): `api-getopts.rs`
     * [std::FromStr](https://doc.rust-lang.org/core/str/trait.FromStr.htmll): `api-std-from_str.rs`

data/username.txt

@@ -0,0 +1 @@
+eliovir

lang-question_mark.rs

@@ -0,0 +1,77 @@
+//! Example of the new operator `?` added in Rust-1.13.0.
+//! See https://blog.rust-lang.org/2016/11/10/Rust-1.13.html
+
+use std::io::prelude::*;
+use std::fs::File;
+use std::io;
+
+fn read_username_from_file() -> Result<String, io::Error> {
+	let mut f = File::open("data/username.txt")?;
+	let mut s = String::new();
+
+	f.read_to_string(&mut s)?;
+
+	Ok(s)
+}
+
+fn read_username_from_file_with_matches() -> Result<String, io::Error> {
+	let f = File::open("data/username.txt");
+	let mut f = match f {
+		Ok(file) => file,
+		Err(e) => return Err(e),
+	};
+
+	let mut s = String::new();
+	match f.read_to_string(&mut s) {
+		Ok(_) => Ok(s),
+		Err(e) => Err(e),
+	}
+}
+
+fn read_username_from_file_with_try() -> Result<String, io::Error> {
+	let mut f = try!(File::open("data/username.txt"));
+	let mut s = String::new();
+
+	try!(f.read_to_string(&mut s));
+
+	Ok(s)
+}
+
+#[cfg(test)]
+mod tests {
+	#[test]
+	fn question_mark() {
+		let found = ::read_username_from_file();
+		assert!(!found.is_err());
+		assert_eq!(found.unwrap(), "eliovir\n".to_string());
+	}
+	#[test]
+	fn with_matches() {
+		let found = ::read_username_from_file_with_matches();
+		assert!(!found.is_err());
+		assert_eq!(found.unwrap(), "eliovir\n".to_string());
+	}
+	#[test]
+	fn with_try() {
+		let found = ::read_username_from_file_with_try();
+		assert!(!found.is_err());
+		assert_eq!(found.unwrap(), "eliovir\n".to_string());
+	}
+}
+
+fn main() {
+	match read_username_from_file() {
+		Ok(s) => println!("The file `data/username.txt` contains `{}`.", s),
+		Err(e) => println!("Something went wrong: {}", e),
+	};
+
+	match read_username_from_file_with_matches() {
+		Ok(s) => println!("The file `data/username.txt` contains `{}`.", s),
+		Err(e) => println!("Something went wrong: {}", e),
+	};
+
+	match read_username_from_file_with_try() {
+		Ok(s) => println!("The file `data/username.txt` contains `{}`.", s),
+		Err(e) => println!("Something went wrong: {}", e),
+	};
+}