pub trait Index<Idx>where
Idx: ?Sized,{
type Output: ?Sized;
// Required method
fn index(&self, index: Idx) -> &Self::Output;
}Expand description
core
Used for indexing operations (container[index]) in immutable contexts.
Re-exported from core::ops::
.
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§
Required Methods§
Implementors§
§impl Index<SpecialCodeIndex> for SpecialCodes
impl Index<SpecialCodeIndex> for SpecialCodes
Source§impl Index<RangeInclusive<usize>> for ByteString
impl Index<RangeInclusive<usize>> for ByteString
Source§impl Index<RangeToInclusive<usize>> for ByteString
impl Index<RangeToInclusive<usize>> for ByteString
§impl<'a, K, V> Index<usize> for Keys<'a, K, V>
Access [IndexMap] keys at indexed positions.
impl<'a, K, V> Index<usize> for Keys<'a, K, V>
Access [IndexMap] keys at indexed positions.
While Index<usize> for IndexMap accesses a map’s values,
indexing through [IndexMap::keys] offers an alternative to access a map’s
keys instead.
Since Keys is also an iterator, consuming items from the iterator will
offset the effective indexes. Similarly, if Keys is obtained from
[Slice::keys], indexes will be interpreted relative to the position of
that slice.
§Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map[0], "LOREM");
assert_eq!(map.keys()[0], "lorem");
assert_eq!(map[1], "IPSUM");
assert_eq!(map.keys()[1], "ipsum");
map.reverse();
assert_eq!(map.keys()[0], "amet");
assert_eq!(map.keys()[1], "sit");
map.sort_keys();
assert_eq!(map.keys()[0], "amet");
assert_eq!(map.keys()[1], "dolor");
// Advancing the iterator will offset the indexing
let mut keys = map.keys();
assert_eq!(keys[0], "amet");
assert_eq!(keys.next().map(|s| &**s), Some("amet"));
assert_eq!(keys[0], "dolor");
assert_eq!(keys[1], "ipsum");
// Slices may have an offset as well
let slice = &map[2..];
assert_eq!(slice[0], "IPSUM");
assert_eq!(slice.keys()[0], "ipsum");use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map.keys()[10]); // panics!§impl<'bump> Index<RangeInclusive<usize>> for devela::_dep::bumpalo::collections::String<'bump>
impl<'bump> Index<RangeInclusive<usize>> for devela::_dep::bumpalo::collections::String<'bump>
§impl<'bump> Index<RangeToInclusive<usize>> for devela::_dep::bumpalo::collections::String<'bump>
impl<'bump> Index<RangeToInclusive<usize>> for devela::_dep::bumpalo::collections::String<'bump>
§impl<'bump, T, I> Index<I> for devela::_dep::bumpalo::collections::Vec<'bump, T>where
I: SliceIndex<[T]>,
impl<'bump, T, I> Index<I> for devela::_dep::bumpalo::collections::Vec<'bump, T>where
I: SliceIndex<[T]>,
type Output = <I as SliceIndex<[T]>>::Output
§impl<'h> Index<usize> for Captures<'h>
Get a matching capture group’s haystack substring by index.
impl<'h> Index<usize> for Captures<'h>
Get a matching capture group’s haystack substring by index.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::get instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
§Panics
If there is no matching group at the given index.
§impl<'h, 'n> Index<&'n str> for Captures<'h>
Get a matching capture group’s haystack substring by name.
impl<'h, 'n> Index<&'n str> for Captures<'h>
Get a matching capture group’s haystack substring by name.
The haystack substring returned can’t outlive the Captures object if this
method is used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it). To work around this limitation, do that, use
Captures::get instead.
'h is the lifetime of the matched haystack, but the lifetime of the
&str returned by this implementation is the lifetime of the Captures
value itself.
'n is the lifetime of the group name used to index the Captures value.
§Panics
If there is no matching group at the given name.
§impl<A, I> Index<I> for SmallVec<A>where
A: Array,
I: SliceIndex<[<A as Array>::Item]>,
impl<A, I> Index<I> for SmallVec<A>where
A: Array,
I: SliceIndex<[<A as Array>::Item]>,
type Output = <I as SliceIndex<[<A as Array>::Item]>>::Output
§impl<I> Index<I> for Bound<'_, PyBytes>where
I: SliceIndex<[u8]>,
This is the same way Vec is indexed.
impl<I> Index<I> for Bound<'_, PyBytes>where
I: SliceIndex<[u8]>,
This is the same way Vec is indexed.
type Output = <I as SliceIndex<[u8]>>::Output
§impl<K, V, Q, S> Index<&Q> for IndexMap<K, V, S>
Access [IndexMap] values corresponding to a key.
impl<K, V, Q, S> Index<&Q> for IndexMap<K, V, S>
Access [IndexMap] values corresponding to a key.
§Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map["lorem"], "LOREM");
assert_eq!(map["ipsum"], "IPSUM");use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map["bar"]); // panics!§impl<K, V, S> Index<usize> for IndexMap<K, V, S>
Access [IndexMap] values at indexed positions.
impl<K, V, S> Index<usize> for IndexMap<K, V, S>
Access [IndexMap] values at indexed positions.
See Index<usize> for Keys to access a map’s keys instead.
§Examples
use indexmap::IndexMap;
let mut map = IndexMap::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
map.insert(word.to_lowercase(), word.to_uppercase());
}
assert_eq!(map[0], "LOREM");
assert_eq!(map[1], "IPSUM");
map.reverse();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "SIT");
map.sort_keys();
assert_eq!(map[0], "AMET");
assert_eq!(map[1], "DOLOR");use indexmap::IndexMap;
let mut map = IndexMap::new();
map.insert("foo", 1);
println!("{:?}", map[10]); // panics!§impl<P, Container> Index<(u32, u32)> for ImageBuffer<P, Container>
impl<P, Container> Index<(u32, u32)> for ImageBuffer<P, Container>
§impl<T, S> Index<usize> for IndexSet<T, S>
Access [IndexSet] values at indexed positions.
impl<T, S> Index<usize> for IndexSet<T, S>
Access [IndexSet] values at indexed positions.
§Examples
use indexmap::IndexSet;
let mut set = IndexSet::new();
for word in "Lorem ipsum dolor sit amet".split_whitespace() {
set.insert(word.to_string());
}
assert_eq!(set[0], "Lorem");
assert_eq!(set[1], "ipsum");
set.reverse();
assert_eq!(set[0], "amet");
assert_eq!(set[1], "sit");
set.sort();
assert_eq!(set[0], "Lorem");
assert_eq!(set[1], "amet");use indexmap::IndexSet;
let mut set = IndexSet::new();
set.insert("foo");
println!("{:?}", set[10]); // panics!