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.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl Index<&Atom> for StringPool

type Output = str

impl Index<Atom> for StringPool

type Output = str

impl Index<ModuleInternedTypeIndex> for ModuleTypes

type Output = WasmSubType

impl Index<Range<usize>> for ByteString

type Output = ByteStr

impl Index<RangeFrom<usize>> for ByteString

type Output = ByteStr

impl Index<RangeFrom<usize>> for CStr

type Output = CStr

impl Index<RangeFrom<usize>> for CStr

type Output = CStr

impl Index<RangeFull> for ByteString

type Output = ByteStr

impl Index<RangeFull> for CString

type Output = CStr

impl Index<RangeFull> for OsString

type Output = OsStr

impl Index<RangeInclusive<usize>> for ByteString

type Output = ByteStr

impl Index<RangeTo<usize>> for ByteString

type Output = ByteStr

impl Index<RangeToInclusive<usize>> for ByteString

type Output = ByteStr

impl Index<TypeComponentIndex> for ComponentTypes

type Output = TypeComponent

impl Index<TypeComponentIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeComponent

impl Index<TypeComponentInstanceIndex> for ComponentTypes

type Output = TypeComponentInstance

impl Index<TypeComponentInstanceIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeComponentInstance

impl Index<TypeComponentLocalErrorContextTableIndex> for ComponentTypes

type Output = TypeErrorContextTable

impl Index<TypeComponentLocalErrorContextTableIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeErrorContextTable

impl Index<TypeEnumIndex> for ComponentTypes

type Output = TypeEnum

impl Index<TypeEnumIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeEnum

impl Index<TypeFixedLengthListIndex> for ComponentTypes

type Output = TypeFixedLengthList

impl Index<TypeFixedLengthListIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeFixedLengthList

impl Index<TypeFlagsIndex> for ComponentTypes

type Output = TypeFlags

impl Index<TypeFlagsIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeFlags

impl Index<TypeFuncIndex> for ComponentTypes

type Output = TypeFunc

impl Index<TypeFuncIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeFunc

impl Index<TypeFutureIndex> for ComponentTypes

type Output = TypeFuture

impl Index<TypeFutureIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeFuture

impl Index<TypeFutureTableIndex> for ComponentTypes

type Output = TypeFutureTable

impl Index<TypeFutureTableIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeFutureTable

impl Index<TypeListIndex> for ComponentTypes

type Output = TypeList

impl Index<TypeListIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeList

impl Index<TypeMapIndex> for ComponentTypes

type Output = TypeMap

impl Index<TypeMapIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeMap

impl Index<TypeModuleIndex> for ComponentTypes

type Output = TypeModule

impl Index<TypeModuleIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeModule

impl Index<TypeOptionIndex> for ComponentTypes

type Output = TypeOption

impl Index<TypeOptionIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeOption

impl Index<TypeRecordIndex> for ComponentTypes

type Output = TypeRecord

impl Index<TypeRecordIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeRecord

impl Index<TypeResourceTableIndex> for ComponentTypes

type Output = TypeResourceTable

impl Index<TypeResourceTableIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeResourceTable

impl Index<TypeResultIndex> for ComponentTypes

type Output = TypeResult

impl Index<TypeResultIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeResult

impl Index<TypeStreamIndex> for ComponentTypes

type Output = TypeStream

impl Index<TypeStreamIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeStream

impl Index<TypeStreamTableIndex> for ComponentTypes

type Output = TypeStreamTable

impl Index<TypeStreamTableIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeStreamTable

impl Index<TypeTupleIndex> for ComponentTypes

type Output = TypeTuple

impl Index<TypeTupleIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeTuple

impl Index<TypeVariantIndex> for ComponentTypes

type Output = TypeVariant

impl Index<TypeVariantIndex> for ComponentTypesBuilder

Available on crate feature compile only.

type Output = TypeVariant

impl Index<usize> for AllocVec

type Output = u8

impl Index<usize> for ByteString

type Output = u8

impl Index<usize> for Slice<'_>

type Output = u8

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

where T: SimdElement, I: SliceIndex<[T]>,

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

impl<I> Index<I> for ByteStr

where I: SliceIndex<ByteStr>,

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

impl<I> Index<I> for String

where I: SliceIndex<str>,

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

impl<I> Index<I> for str

where I: SliceIndex<str>,

type Output = <I as SliceIndex<str>>::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, A> Index<&Q> for wasmtime_environ::collections::oom_abort::HashMap<K, V, S, A>

where K: Eq + Hash + Borrow<Q>, Q: Eq + Hash + ?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, 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> Index<&Q> for wasmtime_environ::prelude::IndexMap<K, V>

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

type Output = V

impl<K, Q, V> Index<&Q> for Map<K, V>

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

type Output = 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, Q, S> Index<&Q> for TryIndexMap<K, V, S>

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

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<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<RangeFull> 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<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<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<usize> for TryIndexMap<K, V, S>

type Output = V

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

type Output = Slice<K, V>

impl<K, V> Index<K> for BoxedSlice<K, V>

where K: EntityRef,

Immutable indexing into a BoxedSlice. The indexed value must be in the map.

type Output = V

impl<K, V> Index<K> for PrimaryMap<K, V>

where K: EntityRef,

Immutable indexing into an PrimaryMap. The indexed value must be in the map.

type Output = V

impl<K, V> Index<K> for SecondaryMap<K, V>

where K: EntityRef, V: Clone,

Immutable indexing into an SecondaryMap.

All keys are permitted. Untouched entries have the default value.

type Output = V

impl<K, V> Index<K> for TryPrimaryMap<K, V>

where K: EntityRef,

type Output = V

impl<K, V> Index<K> for TrySecondaryMap<K, V>

where K: EntityRef, V: Clone,

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<RangeFull> 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<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> Index<usize> for wasmtime_environ::prelude::IndexMap<K, V>

where K: Hash + Eq + Ord,

type Output = V

impl<K, V> Index<usize> for Keys<'_, 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 indices. Similarly, if Keys is obtained from [Slice::keys], indices 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<K, V> Index<usize> for Slice<K, V>

type Output = V

impl<K: EntityRef, V> Index<K> for Intern<K, V>

type Output = V

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

where A: Allocator,

type Output = T

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, I> Index<I> for TryVec<T>

where I: SliceIndex<[T]>,

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

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

where I: SliceIndex<[T]>,

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

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

type Output = Slice<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<RangeFull> 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<RangeTo<usize>> for IndexSet<T, S>

type Output = Slice<T>

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

type Output = Slice<T>

impl<T> Index<Id> for Slab<T>

type Output = T

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

type Output = Slice<T>

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

type Output = Slice<T>

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

type Output = Slice<T>

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

where ModuleTypes: Index<T>,

type Output = <ModuleTypes as Index<T>>::Output

impl<T> Index<T> for ComponentTypesBuilder

where ModuleTypes: Index<T>,

type Output = <ModuleTypes as Index<T>>::Output

impl<T> Index<T> for ModuleTypesBuilder

where ModuleTypes: Index<T>,

type Output = <ModuleTypes as Index<T>>::Output

impl<T> Index<T> for SubtypeArena<'_>

where T: TypeIdentifier,

type Output = <T as TypeIdentifier>::Data

impl<T> Index<T> for Types

where T: TypeIdentifier,

type Output = <T as TypeIdentifier>::Data

impl<T> Index<T> for TypesRef<'_>

where T: TypeIdentifier,

type Output = <T as TypeIdentifier>::Data

impl<T> Index<usize> for wasmtime_environ::prelude::IndexSet<T>

where T: Hash + Eq + Ord,

type Output = T

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

type Output = T