pub trait Index<Idx>where
Idx: ?Sized,{
type Output: ?Sized;
// Required method
fn index(&self, index: Idx) -> &Self::Output;
}std only.Expand description
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§
source§impl Index<Range<usize>> for UninitSlice
impl Index<Range<usize>> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeFrom<usize>> for UninitSlice
impl Index<RangeFrom<usize>> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeFull> for UninitSlice
impl Index<RangeFull> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeInclusive<usize>> for UninitSlice
impl Index<RangeInclusive<usize>> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeInclusive<usize>> for ArchivedString
impl Index<RangeInclusive<usize>> for ArchivedString
source§impl Index<RangeTo<usize>> for UninitSlice
impl Index<RangeTo<usize>> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeToInclusive<usize>> for UninitSlice
impl Index<RangeToInclusive<usize>> for UninitSlice
type Output = UninitSlice
source§impl Index<RangeToInclusive<usize>> for ArchivedString
impl Index<RangeToInclusive<usize>> for ArchivedString
source§impl<'a, K, V> Index<usize> for Keys<'a, K, V>
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!source§impl<K, Q, V, H> Index<&Q> for ArchivedHashMap<K, V, H>
impl<K, Q, V, H> Index<&Q> for ArchivedHashMap<K, V, H>
source§impl<K, V> Index<K> for ArchivedPrimaryMap<K, V>
impl<K, V> Index<K> for ArchivedPrimaryMap<K, V>
Immutable indexing into an ArchivedPrimaryMap.
The indexed value must be in the map.
source§impl<K, V> Index<K> for BoxedSlice<K, V>where
K: EntityRef,
impl<K, V> Index<K> for BoxedSlice<K, V>where
K: EntityRef,
Immutable indexing into a BoxedSlice.
The indexed value must be in the map.
source§impl<K, V> Index<K> for PrimaryMap<K, V>where
K: EntityRef,
impl<K, V> Index<K> for PrimaryMap<K, V>where
K: EntityRef,
Immutable indexing into an PrimaryMap.
The indexed value must be in the map.
source§impl<K, V> Index<K> for SecondaryMap<K, V>
impl<K, V> Index<K> for SecondaryMap<K, V>
Immutable indexing into an SecondaryMap.
All keys are permitted. Untouched entries have the default value.
source§impl<K, V, Q, S> Index<&Q> for IndexMap<K, V, S>
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!source§impl<K, V, S> Index<usize> for IndexMap<K, V, S>
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!source§impl<T, I> Index<I> for ArchivedVec<T>where
I: SliceIndex<[T]>,
impl<T, I> Index<I> for ArchivedVec<T>where
I: SliceIndex<[T]>,
source§impl<T, S> Index<usize> for IndexSet<T, S>
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!