#[lang = "index"]pub trait Index<Idx> where 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.
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);impl Index<Range<usize>> for String[src]
impl Index<RangeFrom<usize>> for CStr[src]
impl Index<RangeFrom<usize>> for String[src]
impl Index<RangeFull> for CString[src]
impl Index<RangeFull> for OsString[src]
impl Index<RangeFull> for String[src]
impl Index<RangeInclusive<usize>> for String[src]
impl Index<RangeTo<usize>> for String[src]
impl Index<RangeToInclusive<usize>> for String[src]
impl<'_, K, Q, V> Index<&'_ Q> for BTreeMap<K, V> where
K: Ord + Borrow<Q>,
Q: Ord + ?Sized, [src]
type Output = Vfn index(&self, key: &Q) -> &VⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Returns a reference to the value corresponding to the supplied key.
Panics if the key is not present in the BTreeMap.
impl<A> Index<usize> for VecDeque<A>[src]
type Output = Afn index(&self, index: usize) -> &AⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<I> Index<I> for str where
I: SliceIndex<str>, [src]
type Output = <I as SliceIndex<str>>::Outputfn index(&self, index: I) -> &<I as SliceIndex<str>>::Output[src]
impl<K, Q: ?Sized, V, S, '_> Index<&'_ Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash,
S: BuildHasher, [src]
type Output = Vfn index(&self, key: &Q) -> &VⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
F: Unpin + Future + ?Sized,
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
I: Iterator + ?Sized,
type Item = <I as Iterator>::Item;
impl<R: Read + ?Sized, '_> Read for &'_ mut R
impl<W: Write + ?Sized, '_> Write for &'_ mut W
[src]
Returns a reference to the value corresponding to the supplied key.
Panics if the key is not present in the HashMap.
impl<T, I> Index<I> for [T] where
I: SliceIndex<[T]>, [src]
type Output = <I as SliceIndex<[T]>>::Outputfn index(&self, index: I) -> &<I as SliceIndex<[T]>>::Output[src]
impl<T, I> Index<I> for Vec<T> where
I: SliceIndex<[T]>, [src]
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/ops/trait.Index.html