pub trait Index<Idx>where
Idx: ?Sized,{
type Output: ?Sized;
// Required method
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§
Dyn Compatibility§
This trait is dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety".
Implementors§
Source§impl Index<Range<usize>> for Wtf8
Returns a slice of the given string for the byte range [begin..end).
impl Index<Range<usize>> for Wtf8
Returns a slice of the given string for the byte range [begin..end).
§Panics
Panics when begin and end do not point to code point boundaries,
or point beyond the end of the string.
Source§impl Index<RangeFrom<usize>> for Wtf8
Returns a slice of the given string from byte begin to its end.
impl Index<RangeFrom<usize>> for Wtf8
Returns a slice of the given string from byte begin to its end.
§Panics
Panics when begin is not at a code point boundary,
or is beyond the end of the string.
Source§impl Index<RangeInclusive<usize>> for ByteString
impl Index<RangeInclusive<usize>> for ByteString
Source§impl Index<RangeTo<usize>> for Wtf8
Returns a slice of the given string from its beginning to byte end.
impl Index<RangeTo<usize>> for Wtf8
Returns a slice of the given string from its beginning to byte end.
§Panics
Panics when end is not at a code point boundary,
or is beyond the end of the string.