Trait scale_info::prelude::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

Looks up a single bit by semantic index.

Examples
use bitvec::prelude::*;

let bits = bits![Msb0, u8; 0, 1, 0];
assert!(!bits[0]); // -----^  |  |
assert!( bits[1]); // --------^  |
assert!(!bits[2]); // -----------^

If the index is greater than or equal to the length, indexing will panic.

The below test will panic when accessing index 1, as only index 0 is valid.

ⓘ
use bitvec::prelude::*;

let bits = bits![0,  ];
bits[1]; // --------^

Implementors