Struct FromFn

pub struct FromFn<Item, State, Next>
where
    Item: HKT,
    Next: FnMut(&mut State) -> Option<Feed<'_, Item>>,
{
    pub state: State,
    pub next: Next,
    pub _phantom: PhantomData<fn(_: &mut State) -> Option<Feed<'_, Item>>>,
}

The impl LendingIterator returned by from_fn().

Example

• use ::lending_iterator::prelude::*;
  
  struct Person {
      name: String,
      age: u8,
  }
  
  fn example (person: &mut Person)
    -> impl '_ + LendingIterator
  /* or:
    -> impl '_ + LendingIteratorDyn<Item = HKT!(&str)>
   */
  {
      lending_iterator::FromFn::<HKT!(&str), _, _> {
          state: person,
          next: |p| if p.age > 0 {
              Some(&p.name)
          } else {
              None
          },
          _phantom: <_>::default(),
      }
  }

Fields

state: State

The state owned by this LendingIterator.

• Think of Self within a manual implementation of the trait;

• Think of repeat_mut().

next: Next

The “fn next()” of a “manual implementation of the trait”.

Trick: since it’s only required to be a closure, this Next closure can capture state on its own, provided it does not need to lend from it.

This can lead to slightly more lightweight FromFn / from_fn calls:

• put the lent / borrowed state inside .state,
• let the rest of the state be implicitly move-captured by this closure.

_phantom: PhantomData<fn(_: &mut State) -> Option<Feed<'_, Item>>>

The signature of fn next in a PhantomData.

Trait Implementations

impl<'next, Item, State, Next> LendingIteratorඞItem<'next> for FromFn<Item, State, Next>

where Item: HKT, Next: FnMut(&mut State) -> Option<Feed<'_, Item>>,

type T = <Item as WithLifetime<'next>>::T

The “output” of this whole hand-rolled GAT: think of LendingIteratorඞItem<'lt>::T as of LendingIterator::Item<'lt>.

impl<Item, State, Next> LendingIterator for FromFn<Item, State, Next>

where Item: HKT, Next: FnMut(&mut State) -> Option<Feed<'_, Item>>,

fn next(self: &mut FromFn<Item, State, Next>) -> Option<Feed<'_, Item>>

Query the next() Item of this Self iterator.

fn filter<F>(self, should_yield: F) -> Filter<Self, F>

where Self: Sized, F: FnMut(&Item<'_, Self>) -> bool,

LendingIterator counterpart of Iterator::filter().

fn for_each(self, f: impl FnMut(Item<'_, Self>))

where Self: Sized,

LendingIterator counterpart of Iterator::for_each().

fn fold<Acc>(self, acc: Acc, f: impl FnMut(Acc, Item<'_, Self>) -> Acc) -> Acc

where Self: Sized,

LendingIterator counterpart of Iterator::fold().

fn try_for_each<Err>( &mut self, f: impl FnMut(Item<'_, Self>) -> Result<(), Err>, ) -> Result<(), Err>

LendingIterator counterpart of Iterator::try_for_each().

fn try_fold<Acc, Err>( &mut self, acc: Acc, f: impl FnMut(Acc, Item<'_, Self>) -> Result<Acc, Err>, ) -> Result<Acc, Err>

LendingIterator counterpart of Iterator::try_fold().

fn all(&mut self, predicate: impl FnMut(Item<'_, Self>) -> bool) -> bool

where Self: Sized,

LendingIterator counterpart of Iterator::all().

fn any(&mut self, predicate: impl FnMut(Item<'_, Self>) -> bool) -> bool

where Self: Sized,

LendingIterator counterpart of Iterator::any().

fn by_ref(&mut self) -> &mut Self

where Self: Sized,

LendingIterator counterpart of Iterator::by_ref().

fn count(self) -> usize

where Self: Sized,

LendingIterator counterpart of Iterator::count().

fn find<'find>( &'find mut self, predicate: impl 'find + FnMut(&Item<'_, Self>) -> bool, ) -> Option<Item<'find, Self>>

where Self: Sized,

LendingIterator counterpart of Iterator::find().

fn fuse(self) -> Fuse<Self>

where Self: Sized,

LendingIterator counterpart of Iterator::fuse().

fn nth(&mut self, n: usize) -> Option<Item<'_, Self>>

LendingIterator counterpart of Iterator::nth().

fn position<F>( &mut self, predicate: impl FnMut(Item<'_, Self>) -> bool, ) -> Option<usize>

where Self: Sized,

LendingIterator counterpart of Iterator::position().

fn skip(self, count: usize) -> Skip<Self>

where Self: Sized,

LendingIterator counterpart of Iterator::skip().

fn take(self, count: usize) -> Take<Self>

where Self: Sized,

LendingIterator counterpart of Iterator::take().

fn map<NewItemType: HKT, F>(self, f: F) -> Map<Self, F, NewItemType>

where for<'next> F: FnMut([&'next Self; 0], Item<'next, Self>) -> Feed<'next, NewItemType>, Self: Sized,

LendingIterator counterpart of Iterator::map().

fn map_to_ref<R: ?Sized, F>(self, f: F) -> Map<Self, F, HKTRef<R>>

where for<'any> F: FnMut([&'any Self; 0], Item<'any, Self>) -> &'any R, Self: Sized,

Convenience method: same as .map(), but for hard-coding the HKT parameter to HKTRef<R> = HKT!(&R).

fn map_to_mut<R: ?Sized, F>(self, f: F) -> Map<Self, F, HKTRefMut<R>>

where for<'any> F: FnMut([&'any Self; 0], Item<'any, Self>) -> &'any mut R, Self: Sized,

Convenience method: same as .map(), but for hard-coding the HKT parameter to HKTRefMut<R> = HKT!(&mut R).

fn map_into_iter<F, NonLendingItem>(self, f: F) -> MapIntoIter<Self, F>

where F: FnMut(Item<'_, Self>) -> NonLendingItem, Self: Sized,

Convenience shorthand for .map…(…).into_iter().

fn filter_map<NewItemType: HKT, F>( self, f: F, ) -> FilterMap<Self, F, NewItemType>

where for<'next> F: FnMut([&'next Self; 0], Item<'next, Self>) -> Option<Feed<'next, NewItemType>>, Self: Sized,

LendingIterator counterpart of Iterator::filter_map().

fn filter_map_to_ref<R: ?Sized, F>(self, f: F) -> FilterMap<Self, F, HKTRef<R>>

where for<'any> F: FnMut([&'any Self; 0], Item<'any, Self>) -> Option<&'any R>, Self: Sized,

Convenience method: same as .filter_map(), but for hard-coding the HKT parameter to HKTRef<R> = HKT!(&R).

fn filter_map_to_mut<R: ?Sized, F>( self, f: F, ) -> FilterMap<Self, F, HKTRefMut<R>>

where for<'any> F: FnMut([&'any Self; 0], Item<'any, Self>) -> Option<&'any mut R>, Self: Sized,

Convenience method: same as .filter_map(), but for hard-coding the HKT parameter to HKTRefMut<R> = HKT!(&mut R).

fn filter_map_into_iter<F, NonLendingItem>( self, f: F, ) -> FilterMapIntoIter<Self, F>

where F: FnMut(Item<'_, Self>) -> Option<NonLendingItem>, Self: Sized,

Convenience shorthand for .filter_map…(…).into_iter().

fn into_iter<Item>(self) -> IntoIter<Self>

where Self: for<'any> LendingIteratorඞItem<'any, T = Item> + Sized,

Convert a Self : LendingIterator into an Iterator, provided Self::Item<'_> does not depend on '_.

fn dyn_boxed<'usability>( self, ) -> Box<dyn LendingIteratorDyn<Item = HKTItem<Self>> + 'usability>

where Self: 'usability + Sized,

Available on crate feature alloc only.

Converts this LendingIterator into a Box<dyn LendingIteratorDyn…>.

fn dyn_boxed_auto<BoxedDynLendingIterator, Item: HKT>( self, ) -> BoxedDynLendingIterator

where Self: Sized + DynCoerce<BoxedDynLendingIterator, Item>,

Available on crate feature alloc only.

Converts this LendingIterator into a Box<dyn LendingIteratorDyn…>.