Struct prev_iter::PrevPeekable
source · pub struct PrevPeekable<I>{ /* private fields */ }
Expand description
Implementations§
source§impl<I> PrevPeekable<I>
impl<I> PrevPeekable<I>
sourcepub fn new(iterator: I) -> Self
pub fn new(iterator: I) -> Self
Creates a new PrevPeekable
. It takes an Iterator
whose Item
implements Clone
.
§Examples
Basic usage:
use prev_iter::PrevPeekable;
let v = vec![1, 2, 3];
let mut iter = PrevPeekable::new(v.iter());
assert_eq!(Some(&1), iter.next());
assert_eq!(Some(&2), iter.next());
assert_eq!(Some(&1), iter.prev());
sourcepub fn peek(&mut self) -> Option<&I::Item>
pub fn peek(&mut self) -> Option<&I::Item>
Returns a reference to the next()
value without advancing the iterator.
Like next
, if there is a value, it is wrapped in a Some(T)
.
But if the iteration is over, None
is returned.
Because peek()
returns a reference, and many iterators iterate over
references, there can be a possibly confusing situation where the
return value is a double reference. You can see this effect in the
examples below.
§Examples
Basic usage:
let xs = [1, 2, 3];
let mut iter = xs.iter().peekable();
// peek() lets us see into the future
assert_eq!(iter.peek(), Some(&&1));
assert_eq!(iter.next(), Some(&1));
assert_eq!(iter.next(), Some(&2));
// The iterator does not advance even if we `peek` multiple times
assert_eq!(iter.peek(), Some(&&3));
assert_eq!(iter.peek(), Some(&&3));
assert_eq!(iter.next(), Some(&3));
// After the iterator is finished, so is `peek()`
assert_eq!(iter.peek(), None);
assert_eq!(iter.next(), None);
sourcepub fn prev(&self) -> Option<I::Item>
pub fn prev(&self) -> Option<I::Item>
Returns the previous value in the iterator without moving the iterator backwards. When the end is reached, it will always return the last element.
This function performs a clone()
when returning the data.
§Examples
Basic usage:
use prev_iter::PrevPeekable;
let v = vec![1, 2];
let mut it = PrevPeekable::new(v.iter());
// When the iterator is initialized there is not previous value
assert_eq!(None, it.prev());
assert_eq!(Some(&1), it.next());
// There is no value before the first element
assert_eq!(None, it.prev());
assert_eq!(Some(&2), it.next());
// Previous value before 2 is 1
assert_eq!(Some(&1), it.prev());
// The iterator doesn't have anymore values so the prev() will always
// return the last element
assert_eq!(None, it.next());
assert_eq!(Some(&2), it.prev());
sourcepub fn prev_peek(&self) -> Option<&I::Item>
pub fn prev_peek(&self) -> Option<&I::Item>
Returns a reference to the previous value in the iterator without moving the iterator backwards. When the end is reached, it will always return the last element.
Because prev_peek()
returns a reference, and many iterators iterate over
references, there can be a possibly confusing situation where the
return value is a double reference. You can see this effect in the
examples below.
§Examples
Basic usage:
use prev_iter::PrevPeekable;
let v = vec![1, 2];
let mut it = PrevPeekable::new(v.iter());
// Initially there is nothing to peek at
assert_eq!(None, it.prev_peek());
assert_eq!(Some(&1), it.next());
// There is nothing before the first element
assert_eq!(None, it.prev_peek());
assert_eq!(Some(&2), it.next());
// 1 comes before 2
assert_eq!(Some(&&1), it.prev_peek());
assert_eq!(None, it.next());
// 2 will always be returned as the last element
assert_eq!(Some(&&2), it.prev_peek());
Trait Implementations§
source§impl<I> Debug for PrevPeekable<I>
impl<I> Debug for PrevPeekable<I>
source§impl<I> Iterator for PrevPeekable<I>
impl<I> Iterator for PrevPeekable<I>
source§fn next(&mut self) -> Option<I::Item>
fn next(&mut self) -> Option<I::Item>
source§fn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
fn next_chunk<const N: usize>(
&mut self
) -> Result<[Self::Item; N], IntoIter<Self::Item, N>>where
Self: Sized,
iter_next_chunk
)N
values. Read more1.0.0 · source§fn size_hint(&self) -> (usize, Option<usize>)
fn size_hint(&self) -> (usize, Option<usize>)
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Self: Sized,
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iter_advance_by
)n
elements. Read more1.0.0 · source§fn nth(&mut self, n: usize) -> Option<Self::Item>
fn nth(&mut self, n: usize) -> Option<Self::Item>
n
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)separator
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Self: Sized,
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iter_map_windows
)f
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,
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)true
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&mut self,
f: F
) -> <<R as Try>::Residual as Residual<Option<<R as Try>::Output>>>::TryType
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)N
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