Trait UnorderedFold 

pub trait UnorderedFold<M, K, V, R>
where
    M: SymmetricFoldMap<K, V>,
    K: Value + Ord,
    V: Value,
{
    // Required methods
    fn add(&mut self, acc: R, key: &K, value: &V) -> R;
    fn remove(&mut self, acc: R, key: &K, value: &V) -> R;
    fn revert_to_init_when_empty(&self) -> bool;

    // Provided methods
    fn update(&mut self, acc: R, key: &K, old: &V, new: &V) -> R { ... }
    fn initial_fold(&mut self, acc: R, input: &M) -> R { ... }
}

Defines an unordered fold for a given map, key, value and output type.

Used with IncrMap::incr_unordered_fold_with.

Implementations get &mut access to self. So you can store things in the type that implements this.

Required Methods

fn add(&mut self, acc: R, key: &K, value: &V) -> R

How to add a key/value pair to the fold value

E.g. |acc, _, value| acc + value for a signed integer.

fn remove(&mut self, acc: R, key: &K, value: &V) -> R

How to remove a key/value pair from the fold value

E.g. |acc, _, value| acc - value for a signed integer.

fn revert_to_init_when_empty(&self) -> bool

If we have emptied the map, can we just reset to the initial value? Or do we have to call remove() on everything that was removed?

Provided Methods

fn update(&mut self, acc: R, key: &K, old: &V, new: &V) -> R

Default implementation is self.add(self.remove(acc, key, old), key, new)

fn initial_fold(&mut self, acc: R, input: &M) -> R

Optimize the initial fold

Implementors

impl<M, K, V, R, FAdd, FRemove, FUpdate, FInitial> UnorderedFold<M, K, V, R> for ClosureFold<M, K, V, R, FAdd, FRemove, FUpdate, FInitial>

where M: SymmetricFoldMap<K, V>, K: Value + Ord, V: Value, R: Value, FAdd: for<'a> FnMut(R, &'a K, &'a V) -> R + 'static + NotObserver, FRemove: for<'a> FnMut(R, &'a K, &'a V) -> R + 'static + NotObserver, FUpdate: for<'a> FnMut(R, &'a K, &'a V, &'a V) -> R + 'static + NotObserver, FInitial: for<'a> FnMut(R, &'a M) -> R + 'static + NotObserver,