Trait nom::lib::std::ops::IndexMut1.0.0[−][src]

#[lang = "index_mut"]pub trait IndexMut<Idx>: Index<Idx> where
    Idx: ?Sized, {
    pub fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
}
[−]

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.

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(&self, index: Side) -> &Self::Output {
        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(&mut self, index: Side) -> &mut Self::Output {
        println!("Accessing {:?}-side of balance mutably", index);
        match index {
            Side::Left => &mut self.left,
            Side::Right => &mut self.right,
        }
    }
}

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

pub fn index_mut(&mut self, index: Idx) -> &mut Self::Output[src][−]

Performs the mutable indexing (container[index]) operation.

Implementations on Foreign Types

impl IndexMut<RangeFull> for OsString[src][−]

impl<T, I> IndexMut<I> for [T] where
    I: SliceIndex<[T]>, [src][−]

impl<I> IndexMut<I> for str where
    I: SliceIndex<str>, [src][−]

impl<T, I, const N: usize> IndexMut<I> for [T; N] where
    [T]: IndexMut<I>, [src][−]

Implementors

impl IndexMut<Range<usize>> for String1.3.0[src][+]

impl IndexMut<RangeFrom<usize>> for String1.3.0[src][+]

impl IndexMut<RangeFull> for String1.3.0[src][+]

impl IndexMut<RangeInclusive<usize>> for String1.26.0[src][+]

impl IndexMut<RangeTo<usize>> for String1.3.0[src][+]

impl IndexMut<RangeToInclusive<usize>> for String1.26.0[src][+]

impl<A> IndexMut<usize> for VecDeque<A>[src][+]

impl<T, I, A> IndexMut<I> for Vec<T, A> where
    I: SliceIndex<[T]>,
    A: Allocator, [src][+]

impl IndexMut<usize> for BStr

impl IndexMut<RangeFull> for BStr

impl IndexMut<Range<usize>> for BStr

impl IndexMut<RangeInclusive<usize>> for BStr

impl IndexMut<RangeFrom<usize>> for BStr

impl IndexMut<RangeTo<usize>> for BStr

impl IndexMut<RangeToInclusive<usize>> for BStr

impl IndexMut<Range<usize>> for UninitSlice

impl IndexMut<RangeFrom<usize>> for UninitSlice

impl IndexMut<RangeFull> for UninitSlice

impl IndexMut<RangeInclusive<usize>> for UninitSlice

impl IndexMut<RangeTo<usize>> for UninitSlice

impl IndexMut<RangeToInclusive<usize>> for UninitSlice

impl<'a, K, V, Q: ?Sized, S> IndexMut<&'a Q> for IndexMap<K, V, S> where
    Q: Hash + Equivalent<K>,
    K: Hash + Eq,
    S: BuildHasher, 

impl<'a, K, V, S, Q: ?Sized> IndexMut<&'a Q> for LinkedHashMap<K, V, S> where
    K: Hash + Eq + Borrow<Q>,
    S: BuildHasher,
    Q: Eq + Hash, 

impl<T: Stackable> IndexMut<usize> for StackRef<T>

impl<T> IndexMut<usize> for RepeatedField<T>

impl<'a, Q: ?Sized> IndexMut<&'a Q> for Map<String, Value> where
    String: Borrow<Q>,
    Q: Ord + Eq + Hash, 

impl<I> IndexMut<I> for Value where
    I: Index, 

impl<T> IndexMut<usize> for Slab<T>

impl<A: Array, I: SliceIndex<[A::Item]>> IndexMut<I> for SmallVec<A>

impl<T, P> IndexMut<usize> for Punctuated<T, P>

impl IndexMut<usize> for LazyBatchColumnVec

impl IndexMut<Range<usize>> for LazyBatchColumnVec

impl IndexMut<RangeTo<usize>> for LazyBatchColumnVec

impl IndexMut<RangeFrom<usize>> for LazyBatchColumnVec

impl<T: MibArg> IndexMut<usize> for Mib<T>

impl<T: MibArg> IndexMut<usize> for MibStr<T>

impl<'a, Q: ?Sized> IndexMut<&'a Q> for Map<String, Value> where
    String: Borrow<Q>,
    Q: Ord + Eq + Hash, 

impl<I> IndexMut<I> for Value where
    I: Index, 

impl<T, I> IndexMut<I> for UncheckedIndex<T> where
    T: GetUncheckedMut<I>, 

impl<V> IndexMut<usize> for VecMap<V>

impl<'a, V> IndexMut<&'a usize> for VecMap<V>