pub enum FocusMut<'a, A> {
// some variants omitted
}
Expand description
A mutable version of Focus
.
See Focus
for more details.
You can only build one FocusMut
at a time for a vector, effectively
keeping a lock on the vector until you’re done with the focus, which relies
on the structure of the vector not changing while it exists.
let mut vec = Vector::from_iter(0..1000);
let focus1 = vec.focus_mut();
// Fails here in 2015 edition because you're creating
// two mutable references to the same thing.
let focus2 = vec.focus_mut();
// Fails here in 2018 edition because creating focus2
// made focus1's lifetime go out of scope.
assert_eq!(Some(&0), focus1.get(0));
On the other hand, you can split that one focus into multiple sub-focuses, which is safe because they can’t overlap:
let mut vec = Vector::from_iter(0..1000);
let focus = vec.focus_mut();
let (mut left, mut right) = focus.split_at(500);
assert_eq!(Some(&0), left.get(0));
assert_eq!(Some(&500), right.get(0));
These sub-foci also work as a lock on the vector, even if the focus they were created from goes out of scope.
let mut vec = Vector::from_iter(0..1000);
let (left, right) = {
let focus = vec.focus_mut();
focus.split_at(500)
};
// `left` and `right` are still in scope even if `focus` isn't, so we can't
// create another focus:
let focus2 = vec.focus_mut();
assert_eq!(Some(&0), left.get(0));
Implementations§
source§impl<'a, A> FocusMut<'a, A>where
A: 'a,
impl<'a, A> FocusMut<'a, A>where
A: 'a,
sourcepub fn narrow<R>(self, range: R) -> Selfwhere
R: RangeBounds<usize>,
pub fn narrow<R>(self, range: R) -> Selfwhere
R: RangeBounds<usize>,
Narrow the focus onto a subslice of the vector.
FocusMut::narrow(range)
has the same effect as &slice[range]
, without
actually modifying the underlying vector.
Panics if the range isn’t fully inside the current focus.
§Examples
let mut vec = Vector::from_iter(0..1000);
let narrowed = vec.focus_mut().narrow(100..200);
let narrowed_vec = narrowed.unmut().into_iter().cloned().collect();
assert_eq!(Vector::from_iter(100..200), narrowed_vec);
sourcepub fn split_at(self, index: usize) -> (Self, Self)
pub fn split_at(self, index: usize) -> (Self, Self)
Split the focus into two.
Given an index index
, consume the focus and produce two new foci, the
left onto indices 0..index
, and the right onto indices index..N
where N
is the length of the current focus.
Panics if the index is out of bounds.
This is the moral equivalent of slice::split_at
, in
that it leaves the underlying data structure unchanged, unlike
Vector::split_at
.
§Examples
let mut vec = Vector::from_iter(0..1000);
{
let (left, right) = vec.focus_mut().split_at(500);
for ptr in left {
*ptr += 100;
}
for ptr in right {
*ptr -= 100;
}
}
let expected = Vector::from_iter(100..600)
+ Vector::from_iter(400..900);
assert_eq!(expected, vec);
source§impl<'a, A> FocusMut<'a, A>where
A: Clone + 'a,
impl<'a, A> FocusMut<'a, A>where
A: Clone + 'a,
sourcepub fn get(&mut self, index: usize) -> Option<&A>
pub fn get(&mut self, index: usize) -> Option<&A>
Get a reference to the value at a given index.
sourcepub fn get_mut(&mut self, index: usize) -> Option<&mut A>
pub fn get_mut(&mut self, index: usize) -> Option<&mut A>
Get a mutable reference to the value at a given index.
sourcepub fn index(&mut self, index: usize) -> &A
pub fn index(&mut self, index: usize) -> &A
Get a reference to the value at a given index.
Panics if the index is out of bounds.
sourcepub fn index_mut(&mut self, index: usize) -> &mut A
pub fn index_mut(&mut self, index: usize) -> &mut A
Get a mutable reference to the value at a given index.
Panics if the index is out of bounds.
sourcepub fn set(&mut self, index: usize, value: A) -> Option<A>
pub fn set(&mut self, index: usize, value: A) -> Option<A>
Update the value at a given index.
Returns None
if the index is out of bounds, or the replaced value
otherwise.
sourcepub fn swap(&mut self, a: usize, b: usize)
pub fn swap(&mut self, a: usize, b: usize)
Swap the values at two given indices.
Panics if either index is out of bounds.
If the indices are equal, this function returns without doing anything.
sourcepub fn pair<F, B>(&mut self, a: usize, b: usize, f: F) -> B
pub fn pair<F, B>(&mut self, a: usize, b: usize, f: F) -> B
Lookup two indices simultaneously and run a function over them.
Useful because the borrow checker won’t let you have more than one mutable reference into the same data structure at any given time.
Panics if either index is out of bounds, or if they are the same index.
§Examples
let mut vec = vector![1, 2, 3, 4, 5];
vec.focus_mut().pair(1, 3, |a, b| *a += *b);
assert_eq!(vector![1, 6, 3, 4, 5], vec);
sourcepub fn triplet<F, B>(&mut self, a: usize, b: usize, c: usize, f: F) -> B
pub fn triplet<F, B>(&mut self, a: usize, b: usize, c: usize, f: F) -> B
Lookup three indices simultaneously and run a function over them.
Useful because the borrow checker won’t let you have more than one mutable reference into the same data structure at any given time.
Panics if any index is out of bounds, or if any indices are equal.
§Examples
let mut vec = vector![1, 2, 3, 4, 5];
vec.focus_mut().triplet(0, 2, 4, |a, b, c| *a += *b + *c);
assert_eq!(vector![9, 2, 3, 4, 5], vec);