Trait std::ops::Index 1.0.0
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[src]
#[lang = "index"]pub trait Index<Idx> where
Idx: ?Sized, { type Output: ?Sized; fn index(&self, index: Idx) -> &Self::Output; }
The Index trait is used to specify the functionality of indexing operations
like container[index] when used in an immutable context.
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 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) -> &usize { 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);Run
Associated Types
Required Methods
fn index(&self, index: Idx) -> &Self::Output
The method for the indexing (container[index]) operation
Implementors
impl Index<RangeFrom<usize>> for Stringimpl<T> Index<RangeToInclusive<usize>> for Vec<T>impl Index<RangeToInclusive<usize>> for Stringimpl Index<RangeFull> for Stringimpl<A> Index<usize> for VecDeque<A>impl<T> Index<RangeFrom<usize>> for Vec<T>impl Index<RangeInclusive<usize>> for Stringimpl<T> Index<usize> for Vec<T>impl<T> Index<RangeTo<usize>> for Vec<T>impl<T> Index<Range<usize>> for Vec<T>impl Index<RangeTo<usize>> for Stringimpl<T> Index<RangeInclusive<usize>> for Vec<T>impl Index<Range<usize>> for Stringimpl<T> Index<RangeFull> for Vec<T>impl<'a, K, Q, V> Index<&'a Q> for BTreeMap<K, V> where
K: Ord + Borrow<Q>,
Q: Ord + ?Sized,impl Index<RangeFrom<usize>> for strimpl Index<RangeTo<usize>> for strimpl Index<RangeFull> for strimpl Index<Range<usize>> for strimpl Index<RangeToInclusive<usize>> for strimpl<T, I> Index<I> for [T] where
I: SliceIndex<[T]>,impl Index<RangeInclusive<usize>> for strimpl<'a, K, Q: ?Sized, V, S> Index<&'a Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash,
S: BuildHasher,impl Index<RangeFull> for CStringimpl Index<RangeFull> for OsString