1.0.0[−][src]Trait std::ops::Index
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);Run
Associated Types
Loading content...Required methods
Loading content...Implementations on Foreign Types
impl<'_, K, Q, V, S> Index<&'_ Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash + ?Sized,
S: BuildHasher,
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash + ?Sized,
S: BuildHasher,
type Output = V
ⓘImportant traits for &'_ mut Ffn index(&self, key: &Q) -> &V
Returns a reference to the value corresponding to the supplied key.
Panics
Panics if the key is not present in the HashMap
.
Implementors
impl Index<Range<usize>> for String
[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]
K: Ord + Borrow<Q>,
Q: Ord + ?Sized,
type Output = V
ⓘImportant traits for &'_ mut Ffn index(&self, key: &Q) -> &V
[src]
Returns a reference to the value corresponding to the supplied key.
Panics
Panics if the key is not present in the BTreeMap
.
impl<'_, K, Q: ?Sized, V, S> Index<&'_ Q> for std::collections::HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash,
S: BuildHasher,
[src]
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash,
S: BuildHasher,
type Output = V
ⓘImportant traits for &'_ mut Ffn index(&self, key: &Q) -> &V
[src]
Returns a reference to the value corresponding to the supplied key.
Panics
Panics if the key is not present in the HashMap
.
impl<A> Index<usize> for VecDeque<A>
[src]
impl<I> Index<I> for str where
I: SliceIndex<str>,
[src]
I: SliceIndex<str>,
type Output = <I as SliceIndex<str>>::Output
fn index(&self, index: I) -> &<I as SliceIndex<str>>::Output
[src]
impl<T, I> Index<I> for [T] where
I: SliceIndex<[T]>,
[src]
I: SliceIndex<[T]>,
type Output = <I as SliceIndex<[T]>>::Output
fn index(&self, index: I) -> &<I as SliceIndex<[T]>>::Output
[src]
impl<T, I> Index<I> for Vec<T> where
I: SliceIndex<[T]>,
[src]
I: SliceIndex<[T]>,