Trait otter_base::imports::Index
1.0.0 · source · [−]pub trait Index<Idx> where
Idx: ?Sized, {
type Output: ?Sized;
fn index(&self, index: Idx) -> &Self::Output;
}
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
sourceimpl<'_, K, Q, V, A> Index<&Q> for BTreeMap<K, V, A> where
A: Allocator + Clone,
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
impl<'_, K, Q, V, A> Index<&Q> for BTreeMap<K, V, A> where
A: Allocator + Clone,
K: Borrow<Q> + Ord,
Q: Ord + ?Sized,
type Output = V
sourceimpl<'_, K, Q, V, S> Index<&Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash + ?Sized,
S: BuildHasher,
impl<'_, K, Q, V, S> Index<&Q> for HashMap<K, V, S> where
K: Eq + Hash + Borrow<Q>,
Q: Eq + Hash + ?Sized,
S: BuildHasher,
type Output = V
sourceimpl<'a, Q> Index<&'a Q> for Map<String, Value> where
Q: Ord + Eq + Hash + ?Sized,
String: Borrow<Q>,
impl<'a, Q> Index<&'a Q> for Map<String, Value> where
Q: Ord + Eq + Hash + ?Sized,
String: Borrow<Q>,
Access an element of this map. Panics if the given key is not present in the map.
match *val {
Value::String(ref s) => Some(s.as_str()),
Value::Array(ref arr) => arr[0].as_str(),
Value::Object(ref map) => map["type"].as_str(),
_ => None,
}