Trait Index

pub trait Index<Idx>
where
    Idx: ?Sized,
{
    type Output: ?Sized;

    // Required method
    fn index(&self, index: Idx) -> &Self::Output;
}

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 the type of value implements Copy.

Examples

The following example implements Index on a read-only NucleotideCount container, enabling individual counts to be retrieved with index syntax.

use std::ops::Index;

enum Nucleotide {
    A,
    C,
    G,
    T,
}

struct NucleotideCount {
    a: usize,
    c: usize,
    g: usize,
    t: usize,
}

impl Index<Nucleotide> for NucleotideCount {
    type Output = usize;

    fn index(&self, nucleotide: Nucleotide) -> &Self::Output {
        match nucleotide {
            Nucleotide::A => &self.a,
            Nucleotide::C => &self.c,
            Nucleotide::G => &self.g,
            Nucleotide::T => &self.t,
        }
    }
}

let nucleotide_count = NucleotideCount {a: 14, c: 9, g: 10, t: 12};
assert_eq!(nucleotide_count[Nucleotide::A], 14);
assert_eq!(nucleotide_count[Nucleotide::C], 9);
assert_eq!(nucleotide_count[Nucleotide::G], 10);
assert_eq!(nucleotide_count[Nucleotide::T], 12);

Required Associated Types

type Output: ?Sized

The returned type after indexing.

Required Methods

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

Performs the indexing (container[index]) operation.

Panics

May panic if the index is out of bounds.

Implementors

impl Index<usize> for FixedBitSet

Return true if the bit is enabled in the bitset, or false otherwise.

Note: bits outside the capacity are always disabled, and thus indexing a FixedBitSet will not panic.

type Output = bool

impl Index<Range<usize>> for UninitSlice

type Output = UninitSlice

impl Index<RangeFrom<usize>> for UninitSlice

type Output = UninitSlice

impl Index<RangeFrom<usize>> for CStr

type Output = CStr

impl Index<RangeInclusive<usize>> for UninitSlice

type Output = UninitSlice

impl Index<RangeFull> for UninitSlice

type Output = UninitSlice

impl Index<RangeFull> for CString

type Output = CStr

impl Index<RangeFull> for OsString

type Output = OsStr

impl Index<RangeTo<usize>> for UninitSlice

type Output = UninitSlice

impl Index<RangeToInclusive<usize>> for UninitSlice

type Output = UninitSlice

impl Index<ConnectionHandle> for Slab<ConnectionMeta>

type Output = ConnectionMeta

impl Index<SpaceId> for [PacketSpace; 3]

type Output = PacketSpace

impl<'a> Index<usize> for InputPair<'a>

type Output = u8

impl<'a, G, I> Index<I> for Frozen<'a, G>

where G: Index<I>,

type Output = <G as Index<I>>::Output

impl<'a, K, V> Index<usize> for Keys<'a, K, V>

Access [IndexMap] keys at indexed positions.

While Index<usize> for IndexMap accesses a map’s values, indexing through [IndexMap::keys] offers an alternative to access a map’s keys instead.

Since Keys is also an iterator, consuming items from the iterator will offset the effective indexes. Similarly, if Keys is obtained from [Slice::keys], indexes will be interpreted relative to the position of that slice.

Examples

use indexmap::IndexMap;

let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    map.insert(word.to_lowercase(), word.to_uppercase());
}

assert_eq!(map[0], "LOREM");
assert_eq!(map.keys()[0], "lorem");
assert_eq!(map[1], "IPSUM");
assert_eq!(map.keys()[1], "ipsum");

map.reverse();
assert_eq!(map.keys()[0], "amet");
assert_eq!(map.keys()[1], "sit");

map.sort_keys();
assert_eq!(map.keys()[0], "amet");
assert_eq!(map.keys()[1], "dolor");

// Advancing the iterator will offset the indexing
let mut keys = map.keys();
assert_eq!(keys[0], "amet");
assert_eq!(keys.next().map(|s| &**s), Some("amet"));
assert_eq!(keys[0], "dolor");
assert_eq!(keys[1], "ipsum");

// Slices may have an offset as well
let slice = &map[2..];
assert_eq!(slice[0], "IPSUM");
assert_eq!(slice.keys()[0], "ipsum");

use indexmap::IndexMap;

let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map.keys()[10]); // panics!

type Output = K

impl<'a, T> Index<usize> for AllocatedStackMemory<'a, T>

type Output = T

impl<'a, T> Index<usize> for HeapPrealloc<'a, T>

where T: 'a,

type Output = [T]

impl<'a, T> Index<Range<usize>> for AllocatedStackMemory<'a, T>

type Output = [T]

impl<'s, T, I> Index<I> for SliceVec<'s, T>

where I: SliceIndex<[T]>,

type Output = <I as SliceIndex<[T]>>::Output

impl<A, I> Index<I> for ArrayVec<A>

where A: Array, I: SliceIndex<[<A as Array>::Item]>,

type Output = <I as SliceIndex<[<A as Array>::Item]>>::Output

impl<A, I> Index<I> for SmallVec<A>

where A: Array, I: SliceIndex<[<A as Array>::Item]>,

type Output = <I as SliceIndex<[<A as Array>::Item]>>::Output

impl<A, I> Index<I> for TinyVec<A>

where A: Array, I: SliceIndex<[<A as Array>::Item]>,

type Output = <I as SliceIndex<[<A as Array>::Item]>>::Output

impl<AllocU32> Index<BucketPopIndex> for EntropyBucketPopulation<AllocU32>

where AllocU32: Allocator<u32>,

type Output = u32

impl<I> Index<I> for str

where I: SliceIndex<str>,

type Output = <I as SliceIndex<str>>::Output

impl<I> Index<I> for String

where I: SliceIndex<str>,

type Output = <I as SliceIndex<str>>::Output

impl<I, T, const N: usize> Index<I> for Simd<T, N>

where T: SimdElement, LaneCount<N>: SupportedLaneCount, I: SliceIndex<[T]>,

type Output = <I as SliceIndex<[T]>>::Output

impl<K, Q, V, A> Index<&Q> for BTreeMap<K, V, A>

where A: Allocator + Clone, K: Borrow<Q> + Ord, Q: Ord + ?Sized,

type Output = V

impl<K, Q, V, S> Index<&Q> for kvarn::prelude::HashMap<K, V, S>

where K: Eq + Hash + Borrow<Q>, Q: Eq + Hash + ?Sized, S: BuildHasher,

type Output = V

impl<K, Q, V, S, A> Index<&Q> for HashMap<K, V, S, A>

where K: Eq + Hash, Q: Hash + Equivalent<K> + ?Sized, S: BuildHasher, A: Allocator,

type Output = V

impl<K, Q, V, S, A> Index<&Q> for HashMap<K, V, S, A>

where K: Eq + Hash, Q: Hash + Equivalent<K> + ?Sized, S: BuildHasher, A: Allocator,

type Output = V

impl<K, T> Index<K> for HeaderMap<T>

where K: AsHeaderName,

type Output = T

impl<K, V> Index<(Bound<usize>, Bound<usize>)> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<usize> for Slice<K, V>

type Output = V

impl<K, V> Index<Range<usize>> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<RangeFrom<usize>> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<RangeInclusive<usize>> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<RangeFull> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<RangeTo<usize>> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V> Index<RangeToInclusive<usize>> for Slice<K, V>

type Output = Slice<K, V>

impl<K, V, Q, S> Index<&Q> for IndexMap<K, V, S>

where Q: Hash + Equivalent<K> + ?Sized, S: BuildHasher,

Access [IndexMap] values corresponding to a key.

Examples

use indexmap::IndexMap;

let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map["lorem"], "LOREM");
assert_eq!(map["ipsum"], "IPSUM");

use indexmap::IndexMap;

let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map["bar"]); // panics!

type Output = V

impl<K, V, S> Index<(Bound<usize>, Bound<usize>)> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<usize> for IndexMap<K, V, S>

Access [IndexMap] values at indexed positions.

See Index<usize> for Keys to access a map’s keys instead.

Examples

use indexmap::IndexMap;

let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map[0], "LOREM");
assert_eq!(map[1], "IPSUM");
map.reverse();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "SIT");
map.sort_keys();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "DOLOR");

use indexmap::IndexMap;

let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map[10]); // panics!

type Output = V

impl<K, V, S> Index<Range<usize>> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<RangeFrom<usize>> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<RangeInclusive<usize>> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<RangeFull> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<RangeTo<usize>> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<K, V, S> Index<RangeToInclusive<usize>> for IndexMap<K, V, S>

type Output = Slice<K, V>

impl<N, E, Ty, Ix> Index<EdgeIndex<Ix>> for StableGraph<N, E, Ty, Ix>

where Ty: EdgeType, Ix: IndexType,

Index the StableGraph by EdgeIndex to access edge weights.

Panics if the edge doesn’t exist.

type Output = E

impl<N, E, Ty, Ix> Index<EdgeIndex<Ix>> for Graph<N, E, Ty, Ix>

where Ty: EdgeType, Ix: IndexType,

Index the Graph by EdgeIndex to access edge weights.

Panics if the edge doesn’t exist.

type Output = E

impl<N, E, Ty, Ix> Index<NodeIndex<Ix>> for StableGraph<N, E, Ty, Ix>

where Ty: EdgeType, Ix: IndexType,

Index the StableGraph by NodeIndex to access node weights.

Panics if the node doesn’t exist.

type Output = N

impl<N, E, Ty, Ix> Index<NodeIndex<Ix>> for Graph<N, E, Ty, Ix>

where Ty: EdgeType, Ix: IndexType,

Index the Graph by NodeIndex to access node weights.

Panics if the node doesn’t exist.

type Output = N

impl<N, E, Ty, Ix> Index<Ix> for Csr<N, E, Ty, Ix>

where Ty: EdgeType, Ix: IndexType,

type Output = N

impl<N, E, Ty, Null, Ix> Index<(NodeIndex<Ix>, NodeIndex<Ix>)> for MatrixGraph<N, E, Ty, Null, Ix>

where Ty: EdgeType, Null: Nullable<Wrapped = E>, Ix: IndexType,

Index the MatrixGraph by NodeIndex pair to access edge weights.

Also available with indexing syntax: &graph[e].

Panics if no edge exists between a and b.

type Output = E

impl<N, E, Ty, Null, Ix> Index<NodeIndex<Ix>> for MatrixGraph<N, E, Ty, Null, Ix>

where Ty: EdgeType, Null: Nullable<Wrapped = E>, Ix: IndexType,

Index the MatrixGraph by NodeIndex to access node weights.

Panics if the node doesn’t exist.

type Output = N

impl<N, E, Ty, S> Index<(N, N)> for GraphMap<N, E, Ty, S>

where N: NodeTrait, Ty: EdgeType, S: BuildHasher,

Index GraphMap by node pairs to access edge weights.

type Output = E

impl<T> Index<(Bound<usize>, Bound<usize>)> for Slice<T>

type Output = Slice<T>

impl<T> Index<usize> for Slab<T>

type Output = T

impl<T> Index<usize> for Slice<T>

type Output = T

impl<T> Index<usize> for WrapBox<T>

type Output = T

impl<T> Index<Range<usize>> for Slice<T>

type Output = Slice<T>

impl<T> Index<Range<usize>> for WrapBox<T>

type Output = [T]

impl<T> Index<RangeFrom<usize>> for Slice<T>

type Output = Slice<T>

impl<T> Index<RangeInclusive<usize>> for Slice<T>

type Output = Slice<T>

impl<T> Index<RangeFull> for Slice<T>

type Output = Slice<T>

impl<T> Index<RangeTo<usize>> for Slice<T>

type Output = Slice<T>

impl<T> Index<RangeToInclusive<usize>> for Slice<T>

type Output = Slice<T>

impl<T, A> Index<usize> for VecDeque<T, A>

where A: Allocator,

type Output = T

impl<T, I> Index<I> for [T]

where I: SliceIndex<[T]>,

type Output = <I as SliceIndex<[T]>>::Output

impl<T, I, A> Index<I> for Vec<T, A>

where I: SliceIndex<[T]>, A: Allocator,

type Output = <I as SliceIndex<[T]>>::Output

impl<T, I, const N: usize> Index<I> for [T; N]

where [T]: Index<I>,

type Output = <[T] as Index<I>>::Output

impl<T, S> Index<(Bound<usize>, Bound<usize>)> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<usize> for IndexSet<T, S>

Access [IndexSet] values at indexed positions.

Examples

use indexmap::IndexSet;

let mut set = IndexSet::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
    set.insert(word.to_string());
}
assert_eq!(set[0], "Lorem");
assert_eq!(set[1], "ipsum");
set.reverse();
assert_eq!(set[0], "amet");
assert_eq!(set[1], "sit");
set.sort();
assert_eq!(set[0], "Lorem");
assert_eq!(set[1], "amet");

use indexmap::IndexSet;

let mut set = IndexSet::new();
set.insert("foo");
println!("{:?}", set[10]); // panics!

type Output = T

impl<T, S> Index<Range<usize>> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<RangeFrom<usize>> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<RangeInclusive<usize>> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<RangeFull> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<RangeTo<usize>> for IndexSet<T, S>

type Output = Slice<T>

impl<T, S> Index<RangeToInclusive<usize>> for IndexSet<T, S>

type Output = Slice<T>