Trait wasmtime_environ::__core::ops::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);

Associated Types

The returned type after indexing.

Required methods

Performs the indexing (container[index]) operation.

Panics

May panic if the index is out of bounds.

Implementations on Foreign Types

Returns a reference to the value corresponding to the supplied key.

Panics

Panics if the key is not present in the HashMap.

Returns a reference to the value corresponding to the supplied key.

Panics

Panics if the key is not present in the BTreeMap.

Access IndexMap values at indexed positions.

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!

Returns a reference to the value at the supplied index.

Panics if index is out of bounds.

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!

Returns a reference to the value at the supplied index.

Panics if index is out of bounds.

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!

Returns a reference to the value corresponding to the supplied key.

Panics if key is not present in the map.

Returns a reference to the value corresponding to the supplied key.

Panics

Panics if the key is not present in the HashMap.

Implementors

Immutable indexing into a BoxedSlice. The indexed value must be in the map.

Immutable indexing into an PrimaryMap. The indexed value must be in the map.

Immutable indexing into an SecondaryMap.

All keys are permitted. Untouched entries have the default value.