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<RangeFrom<usize>> for CStr

type Output = CStr

impl Index<RangeFull> for CString

type Output = CStr

impl Index<RangeFull> for OsString

type Output = OsStr

impl<A, O, Idx> Index<Idx> for BitArray<A, O>

where A: BitViewSized, O: BitOrder, BitSlice<<A as BitView>::Store, O>: Index<Idx>,

type Output = <BitSlice<<A as BitView>::Store, O> as Index<Idx>>::Output

impl<F> Index<usize> for DenseMultilinearPolynomial<F>

where F: IsField, <F as IsField>::BaseType: Send + Sync,

type Output = FieldElement<F>

impl<I> Index<I> for Value

where I: Index,

type Output = Value

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 cairo_vm::with_std::collections::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 hashbrown::map::HashMap<K, V, S, A>

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

type Output = V

impl<Q> Index<&Q> for Map<String, Value>

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

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

match val {
    Value::String(s) => Some(s.as_str()),
    Value::Array(arr) => arr[0].as_str(),
    Value::Object(map) => map["type"].as_str(),
    _ => None,
}

type Output = Value

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 cairo_vm::stdlib::prelude::Vec<T, A>

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

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

impl<T, I, A> Index<I> for allocator_api2::stable::vec::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, O> Index<usize> for BitSlice<T, O>

where T: BitStore, O: BitOrder,

type Output = bool

impl<T, O> Index<Range<usize>> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O> Index<RangeFrom<usize>> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O> Index<RangeFull> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O> Index<RangeInclusive<usize>> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O> Index<RangeTo<usize>> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O> Index<RangeToInclusive<usize>> for BitSlice<T, O>

where O: BitOrder, T: BitStore,

type Output = BitSlice<T, O>

impl<T, O, Idx> Index<Idx> for BitBox<T, O>

where T: BitStore, O: BitOrder, BitSlice<T, O>: Index<Idx>,

type Output = <BitSlice<T, O> as Index<Idx>>::Output

impl<T, O, Idx> Index<Idx> for BitVec<T, O>

where T: BitStore, O: BitOrder, BitSlice<T, O>: Index<Idx>,

type Output = <BitSlice<T, O> as Index<Idx>>::Output