Trait geng_core::prelude::IndexMut

#[lang = "index_mut"]pub trait IndexMut<Idx>: Index<Idx> where
    Idx: ?Sized, {
    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

fn index_mut(&mut self, index: Idx) -> &mut Self::Output

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

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Implementations on Foreign Types

impl IndexMut<RangeFull> for OsString

fn index_mut(&mut self, _index: RangeFull) -> &mut OsStr

impl<I> IndexMut<I> for str where
    I: SliceIndex<str>, 

fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<str>>::Output

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

fn index_mut(&mut self, index: I) -> &mut <I as SliceIndex<[T]>>::Output

impl IndexMut<RangeFrom<usize>> for String

fn index_mut(&mut self, index: RangeFrom<usize>) -> &mut str

impl IndexMut<RangeInclusive<usize>> for String

fn index_mut(&mut self, index: RangeInclusive<usize>) -> &mut str

impl IndexMut<RangeTo<usize>> for String

fn index_mut(&mut self, index: RangeTo<usize>) -> &mut str

impl IndexMut<Range<usize>> for String

fn index_mut(&mut self, index: Range<usize>) -> &mut str

impl IndexMut<RangeToInclusive<usize>> for String

fn index_mut(&mut self, index: RangeToInclusive<usize>) -> &mut str

impl IndexMut<RangeFull> for String

fn index_mut(&mut self, _index: RangeFull) -> &mut str

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

fn index_mut(&mut self, index: I) -> &mut <Vec<T> as Index<I>>::Outputⓘ

Important traits for Vec<u8>

impl Write for Vec<u8>

impl<A> IndexMut<usize> for VecDeque<A>

fn index_mut(&mut self, index: usize) -> &mut Aⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

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

fn index_mut(&mut self, key: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

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

fn index_mut(&mut self, i: usize) -> &mut Vⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

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

fn index_mut(&mut self, i: &usize) -> &mut Vⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<'_> IndexMut<&'_ Value> for Map

fn index_mut(&mut self, index: &Value) -> &mut <Map as Index<&'_ Value>>::Output

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

fn index_mut(
    &mut self,
    index: I
) -> &mut <I as SliceIndex<[<A as Array>::Item]>>::Output

impl<T> IndexMut<usize> for LumaA<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<T> IndexMut<usize> for Rgb<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<Buffer> IndexMut<(u8, u32, u32)> for FlatSamples<Buffer> where
    Buffer: IndexMut<usize>, 

fn index_mut(
    &mut self,
    (u8, u32, u32)
) -> &mut <FlatSamples<Buffer> as Index<(u8, u32, u32)>>::Output

Return a mutable reference to a single sample at specified coordinates.

Panics

When the coordinates are out of bounds or the index calculation fails.

impl<T> IndexMut<usize> for Luma<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<T> IndexMut<usize> for Bgra<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<T> IndexMut<usize> for Rgba<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<P, Container> IndexMut<(u32, u32)> for ImageBuffer<P, Container> where
    Container: Deref<Target = [<P as Pixel>::Subpixel]> + DerefMut,
    P: Pixel + 'static,
    <P as Pixel>::Subpixel: 'static, 

fn index_mut(&mut self, (u32, u32)) -> &mut Pⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<T> IndexMut<usize> for Bgr<T> where
    T: Primitive, 

fn index_mut(&mut self, _index: usize) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

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, 

fn index_mut(&mut self, index: &'a Q) -> &mut Vⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

impl<A, I> IndexMut<I> for ArrayVec<A> where
    A: Array,
    I: SliceIndex<[<A as Array>::Item]>, 

#[must_use]fn index_mut(&mut self, index: I) -> &mut <ArrayVec<A> as Index<I>>::Output

impl<A, I> IndexMut<I> for TinyVec<A> where
    A: Array,
    I: SliceIndex<[<A as Array>::Item]>, 

#[must_use]fn index_mut(&mut self, index: I) -> &mut <TinyVec<A> as Index<I>>::Output

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Implementors

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

Mutably access an element of this map. Panics if the given key is not present in the map.

map["key"] = json!("value");

fn index_mut(&mut self, index: &Q) -> &mut Value

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

fn index_mut(&mut self, index: I) -> &mut Value

Write into a serde_json::Value using the syntax value[0] = ... or value["k"] = ....

If the index is a number, the value must be an array of length bigger than the index. Indexing into a value that is not an array or an array that is too small will panic.

If the index is a string, the value must be an object or null which is treated like an empty object. If the key is not already present in the object, it will be inserted with a value of null. Indexing into a value that is neither an object nor null will panic.

Examples

let mut data = json!({ "x": 0 });

// replace an existing key
data["x"] = json!(1);

// insert a new key
data["y"] = json!([false, false, false]);

// replace an array value
data["y"][0] = json!(true);

// inserted a deeply nested key
data["a"]["b"]["c"]["d"] = json!(true);

println!("{}", data);

impl<T> IndexMut<(usize, usize)> for Mat4<T>

fn index_mut(&mut self, (usize, usize)) -> &mut Tⓘ

Important traits for &'_ mut R

impl<'_, R> Read for &'_ mut R where
    R: Read + ?Sized, impl<'_, W> Write for &'_ mut W where
    W: Write + ?Sized, impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,  type Item = <I as Iterator>::Item;impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,  type Output = <F as Future>::Output;

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