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§
Implementors§
source§impl<'t> Index<usize> for regex::re_bytes::Captures<'t>
impl<'t> Index<usize> for regex::re_bytes::Captures<'t>
Get a group by index.
't is the lifetime of the matched text.
The text can’t outlive the Captures object if this method is
used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it); to do that, use get() instead.
Panics
If there is no group at the given index.
source§impl<'t> Index<usize> for regex::re_unicode::Captures<'t>
impl<'t> Index<usize> for regex::re_unicode::Captures<'t>
Get a group by index.
't is the lifetime of the matched text.
The text can’t outlive the Captures object if this method is
used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it); to do that, use get() instead.
Panics
If there is no group at the given index.
source§impl<'t, 'i> Index<&'i str> for regex::re_bytes::Captures<'t>
impl<'t, 'i> Index<&'i str> for regex::re_bytes::Captures<'t>
Get a group by name.
't is the lifetime of the matched text and 'i is the lifetime
of the group name (the index).
The text can’t outlive the Captures object if this method is
used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it); to do that, use name instead.
Panics
If there is no group named by the given value.
source§impl<'t, 'i> Index<&'i str> for regex::re_unicode::Captures<'t>
impl<'t, 'i> Index<&'i str> for regex::re_unicode::Captures<'t>
Get a group by name.
't is the lifetime of the matched text and 'i is the lifetime
of the group name (the index).
The text can’t outlive the Captures object if this method is
used, because of how Index is defined (normally a[i] is part
of a and can’t outlive it); to do that, use name instead.
Panics
If there is no group named by the given value.