Trait core::ops::Index 1.0.0[−][src]
#[lang = "index"]pub trait Index<Idx: ?Sized> { type Output: ?Sized; 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) -> &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
Implementors
impl<T, I> Index<I> for [T] where
I: SliceIndex<[T]>, type Output = I::Output;impl Index<Range<usize>> for str type Output = str;impl Index<RangeTo<usize>> for str type Output = str;impl Index<RangeFrom<usize>> for str type Output = str;impl Index<RangeFull> for str type Output = str;impl Index<RangeInclusive<usize>> for str type Output = str;impl Index<RangeToInclusive<usize>> for str type Output = str;