Trait ethcore_util::standard::ops::IndexMut 1.0.0
[−]
[src]
pub trait IndexMut<Idx>: Index<Idx> where Idx: ?Sized {
fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
}
The IndexMut
trait is used to specify the functionality of indexing
operations like container[index]
when used in a mutable context.
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
.
Examples
A very simple implementation of a Balance
struct that has two sides, where
each can be indexed mutably and immutably.
use std::ops::{Index,IndexMut}; #[derive(Debug)] enum Side { Left, Right, } #[derive(Debug, PartialEq)] enum Weight { Kilogram(f32), Pound(f32), } struct Balance { pub left: Weight, pub right:Weight, } impl Index<Side> for Balance { type Output = Weight; fn index<'a>(&'a self, index: Side) -> &'a Weight { println!("Accessing {:?}-side of balance immutably", index); match index { Side::Left => &self.left, Side::Right => &self.right, } } } impl IndexMut<Side> for Balance { fn index_mut<'a>(&'a mut self, index: Side) -> &'a mut Weight { println!("Accessing {:?}-side of balance mutably", index); match index { Side::Left => &mut self.left, Side::Right => &mut self.right, } } } fn main() { 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)); // 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); }
Required Methods
fn index_mut(&mut self, index: Idx) -> &mut Self::Output
The method for the mutable indexing (container[index]
) operation
Implementors
impl IndexMut<Range<usize>> for String
impl IndexMut<RangeTo<usize>> for String
impl IndexMut<RangeFrom<usize>> for String
impl IndexMut<RangeFull> for String
impl IndexMut<RangeInclusive<usize>> for String
impl IndexMut<RangeToInclusive<usize>> for String
impl<T> IndexMut<usize> for Vec<T>
impl<T> IndexMut<Range<usize>> for Vec<T>
impl<T> IndexMut<RangeTo<usize>> for Vec<T>
impl<T> IndexMut<RangeFrom<usize>> for Vec<T>
impl<T> IndexMut<RangeFull> for Vec<T>
impl<T> IndexMut<RangeInclusive<usize>> for Vec<T>
impl<T> IndexMut<RangeToInclusive<usize>> for Vec<T>
impl<A> IndexMut<usize> for VecDeque<A>
impl<A> IndexMut<usize> for SmallVec<A> where A: Array
impl<A> IndexMut<Range<usize>> for SmallVec<A> where A: Array
impl<A> IndexMut<RangeFrom<usize>> for SmallVec<A> where A: Array
impl<A> IndexMut<RangeTo<usize>> for SmallVec<A> where A: Array
impl<A> IndexMut<RangeFull> for SmallVec<A> where A: Array
impl IndexMut<usize> for H32
impl IndexMut<Range<usize>> for H32
impl IndexMut<RangeFull> for H32
impl IndexMut<usize> for H64
impl IndexMut<Range<usize>> for H64
impl IndexMut<RangeFull> for H64
impl IndexMut<usize> for H128
impl IndexMut<Range<usize>> for H128
impl IndexMut<RangeFull> for H128
impl IndexMut<usize> for H160
impl IndexMut<Range<usize>> for H160
impl IndexMut<RangeFull> for H160
impl IndexMut<usize> for H256
impl IndexMut<Range<usize>> for H256
impl IndexMut<RangeFull> for H256
impl IndexMut<usize> for H264
impl IndexMut<Range<usize>> for H264
impl IndexMut<RangeFull> for H264
impl IndexMut<usize> for H512
impl IndexMut<Range<usize>> for H512
impl IndexMut<RangeFull> for H512
impl IndexMut<usize> for H520
impl IndexMut<Range<usize>> for H520
impl IndexMut<RangeFull> for H520
impl IndexMut<usize> for H1024
impl IndexMut<Range<usize>> for H1024
impl IndexMut<RangeFull> for H1024
impl IndexMut<usize> for H2048
impl IndexMut<Range<usize>> for H2048
impl IndexMut<RangeFull> for H2048
impl<T> IndexMut<usize> for [T]
impl<T> IndexMut<Range<usize>> for [T]
impl<T> IndexMut<RangeTo<usize>> for [T]
impl<T> IndexMut<RangeFrom<usize>> for [T]
impl<T> IndexMut<RangeFull> for [T]
impl<T> IndexMut<RangeInclusive<usize>> for [T]
impl<T> IndexMut<RangeToInclusive<usize>> for [T]
impl IndexMut<Range<usize>> for str
impl IndexMut<RangeTo<usize>> for str
impl IndexMut<RangeFrom<usize>> for str
impl IndexMut<RangeFull> for str
impl IndexMut<RangeInclusive<usize>> for str
impl IndexMut<RangeToInclusive<usize>> for str
impl<'a, A> IndexMut<usize> for StrideMut<'a, A>
impl<'a, K, V, S, Q> IndexMut<&'a Q> for LinkedHashMap<K, V, S> where K: Hash + Eq + Borrow<Q>, Q: Eq + Hash + ?Sized, S: BuildHasher