Fix rational_numbers example (from_str now returns Result, not Option).

Also: Remove warning about unnecessary `mut`.

examples/rational_numbers.rs

@@ -1,7 +1,7 @@
 //! This example shows how to write your own custom implementation of
 //! `Decodable` to parse rational numbers.
 
-#![feature(collections, core)]
+#![feature(core)]
 
 extern crate csv;
 extern crate regex;
@@ -23,22 +23,27 @@ impl Decodable for Rational {
  let field = try!(d.read_str());
  // This uses the `FromStr` impl below.
  match field.parse() {
- Some(rat) => Ok(rat),
- None => Err(d.error(&*format!(
+ Ok(rat) => Ok(rat),
+ Err(_) => Err(d.error(&*format!(
  "Could not parse '{}' as a rational.", field))),
  }
  }
 }
 
 impl str::FromStr for Rational {
+ type Err = csv::Error;
+
  /// Parse a string into a Rational. Allow for the possibility of whitespace
  /// around `/`.
- fn from_str(s: &str) -> Option<Rational> {
+ fn from_str(s: &str) -> Result<Rational, csv::Error> {
  let re = Regex::new(r"^([0-9]+)\s*/\s*([0-9]+)$").unwrap();
- re.captures(s).map(|caps| Rational {
+ match re.captures(s).map(|caps| Rational {
  numerator: caps.at(1).unwrap().parse().unwrap(),
  denominator: caps.at(2).unwrap().parse().unwrap(),
- })
+ }) {
+ Some(r) => Ok(r),
+ None => Err(csv::Error::Encode(format!("Failed to parse Rational {}", s))),
+ }
  }
 }
 

src/writer.rs

@@ -239,7 +239,7 @@ impl<W: io::Writer> Writer<W> {
  /// Writes a record of results. If any of the results resolve to an error,
  /// then writing stops and that error is returned.
  #[doc(hidden)]
- pub fn write_iter<'a, I, F>(&mut self, mut r: I) -> CsvResult<()>
+ pub fn write_iter<'a, I, F>(&mut self, r: I) -> CsvResult<()>
  where I: Iterator<Item=CsvResult<F>>, F: BorrowBytes {
  let delim = self.delimiter;
  let mut count = 0;