`reader.read_line()` includes trailing newline char, which makes
`from_str` always return `None`.
/// let line: IoResult<String> = reader.read_line();
/// // Convert the string line to a number using `map` and `from_str`
/// let val: IoResult<int> = line.map(|line| {
- /// from_str::<int>(line.as_slice()).unwrap_or(0)
+ /// from_str::<int>(line.as_slice().trim_right()).unwrap_or(0)
/// });
/// // Add the value if there were no errors, otherwise add 0
/// sum += val.ok().unwrap_or(0);
/// }
+ ///
+ /// assert!(sum == 10);
/// ~~~
#[inline]
pub fn map<U>(self, op: |T| -> U) -> Result<U,E> {