Improve doc example for `std::borrow::Cow`.
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@ -86,16 +86,29 @@ impl<T> ToOwned for T where T: Clone {
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/// ```
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/// use std::borrow::Cow;
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///
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/// # #[allow(dead_code)]
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/// fn abs_all(input: &mut Cow<[i32]>) {
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/// for i in 0..input.len() {
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/// let v = input[i];
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/// if v < 0 {
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/// // clones into a vector the first time (if not already owned)
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/// // Clones into a vector if not already owned.
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/// input.to_mut()[i] = -v;
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/// }
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/// }
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/// }
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///
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/// // No clone occurs because `input` doesn't need to be mutated.
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/// let slice = [0, 1, 2];
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/// let mut input = Cow::from(&slice[..]);
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/// abs_all(&mut input);
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///
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/// // Clone occurs because `input` needs to be mutated.
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/// let slice = [-1, 0, 1];
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/// let mut input = Cow::from(&slice[..]);
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/// abs_all(&mut input);
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///
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/// // No clone occurs because `input` is already owned.
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/// let mut input = Cow::from(vec![-1, 0, 1]);
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/// abs_all(&mut input);
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/// ```
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#[stable(feature = "rust1", since = "1.0.0")]
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pub enum Cow<'a, B: ?Sized + 'a>
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