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Revise Index and IndexMut docs.

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Part of #29365.
* Shortened summary sentences, removing "stuttering"
* Small copyediting
* Changed method summary sentences to be in 3rd person singular
* Removed extraneous explicit `fn main()` in example for `IndexMut`
This commit is contained in:
lukaramu 2017-08-07 19:57:32 +02:00
parent 4b945fd9fe
commit ffa327b3a4
1 changed files with 21 additions and 24 deletions
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45
src/libcore/ops/index.rs
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@ -8,13 +8,12 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
/// The `Index` trait is used to specify the functionality of indexing operations
/// like `container[index]` when used in an immutable context.
/// Used for indexing operations (`container[index]`) in immutable contexts.
///
/// `container[index]` is actually syntactic sugar for `*container.index(index)`,
/// but only when used as an immutable value. If a mutable value is requested,
/// [`IndexMut`] is used instead. This allows nice things such as
/// `let value = v[index]` if `value` implements [`Copy`].
/// `let value = v[index]` if the type of `value` implements [`Copy`].
///
/// [`IndexMut`]: ../../std/ops/trait.IndexMut.html
/// [`Copy`]: ../../std/marker/trait.Copy.html
@ -64,22 +63,22 @@
#[rustc_on_unimplemented = "the type `{Self}` cannot be indexed by `{Idx}`"]
#[stable(feature = "rust1", since = "1.0.0")]
pub trait Index<Idx: ?Sized> {
/// The returned type after indexing
/// The returned type after indexing.
#[stable(feature = "rust1", since = "1.0.0")]
type Output: ?Sized;
/// The method for the indexing (`container[index]`) operation
/// Performs the indexing (`container[index]`) operation.
#[stable(feature = "rust1", since = "1.0.0")]
fn index(&self, index: Idx) -> &Self::Output;
}
/// The `IndexMut` trait is used to specify the functionality of indexing
/// operations like `container[index]` when used in a mutable context.
/// Used for indexing operations (`container[index]`) in mutable contexts.
///
/// `container[index]` is actually syntactic sugar for
/// `*container.index_mut(index)`, but only when used as a mutable value. If
/// an immutable value is requested, the [`Index`] trait is used instead. This
/// allows nice things such as `v[index] = value` if `value` implements [`Copy`].
/// allows nice things such as `v[index] = value` if the type of `value`
/// implements [`Copy`].
///
/// [`Index`]: ../../std/ops/trait.Index.html
/// [`Copy`]: ../../std/marker/trait.Copy.html
@ -106,7 +105,7 @@ pub trait Index<Idx: ?Sized> {
///
/// struct Balance {
/// pub left: Weight,
/// pub right:Weight,
/// pub right: Weight,
/// }
///
/// impl Index<Side> for Balance {
@ -131,28 +130,26 @@ pub trait Index<Idx: ?Sized> {
/// }
/// }
///
/// fn main() {
/// let mut balance = Balance {
/// right: Weight::Kilogram(2.5),
/// left: Weight::Pound(1.5),
/// };
/// let mut balance = Balance {
/// right: Weight::Kilogram(2.5),
/// left: Weight::Pound(1.5),
/// };
///
/// // In this case balance[Side::Right] is sugar for
/// // *balance.index(Side::Right), since we are only reading
/// // balance[Side::Right], not writing it.
/// assert_eq!(balance[Side::Right],Weight::Kilogram(2.5));
/// // In this case, `balance[Side::Right]` is sugar for
/// // `*balance.index(Side::Right)`, since we are only *reading*
/// // `balance[Side::Right]`, not writing it.
/// assert_eq!(balance[Side::Right], Weight::Kilogram(2.5));
///
/// // However in this case balance[Side::Left] is sugar for
/// // *balance.index_mut(Side::Left), since we are writing
/// // balance[Side::Left].
/// balance[Side::Left] = Weight::Kilogram(3.0);
/// }
/// // However, in this case `balance[Side::Left]` is sugar for
/// // `*balance.index_mut(Side::Left)`, since we are writing
/// // `balance[Side::Left]`.
/// balance[Side::Left] = Weight::Kilogram(3.0);
/// ```
#[lang = "index_mut"]
#[rustc_on_unimplemented = "the type `{Self}` cannot be mutably indexed by `{Idx}`"]
#[stable(feature = "rust1", since = "1.0.0")]
pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
/// The method for the mutable indexing (`container[index]`) operation
/// Performs the mutable indexing (`container[index]`) operation.
#[stable(feature = "rust1", since = "1.0.0")]
fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
}