Enum MergeResult

pub enum MergeResult<K, V> {
    EmitLeft,
    Other {
        emit: Option<BoxedItem<K, V>>,
        left: ItemOp<K, V>,
        right: ItemOp<K, V>,
    },
}

Variants

EmitLeft

Emits the left item unchanged. Keeps the right item. This is the common case. Once an item has been emitted, it will never be seen again by the merge function.

Other

All other merge results are covered by the following. Take care when replacing items that you replace the correct item. The merger will never merge two items together from the same layer. Consider the following scenario:

   +-----------+              +-----------+

0: | A | | C | +———–+–––––––+———–+ 1: | B | +–––––––+

Let’s say that all three items can be merged together. The merge function will first be presented with items A and B, at which point it has the option of replacing the left item (i.e. A, in layer 0) or the right item (i.e. B in layer 1). However, if you replace the left item, the merge function will not then be given the opportunity to merge it with C, so the correct thing to do in this case is to replace the right item B in layer 1, and discard the left item. A rule you can use is that you should avoid replacing an item with another item whose upper bound exceeds that of the item you are replacing.

There are some combinations that might lead to infinite loops (e.g. None, Keep, Keep) and should obviously be avoided.

Fields

emit: Option<BoxedItem<K, V>>

left: ItemOp<K, V>

right: ItemOp<K, V>

Trait Implementations

impl<K: Debug, V: Debug> Debug for MergeResult<K, V>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<K: PartialEq, V: PartialEq> PartialEq for MergeResult<K, V>

fn eq(&self, other: &MergeResult<K, V>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<K: Eq, V: Eq> Eq for MergeResult<K, V>

impl<K, V> StructuralPartialEq for MergeResult<K, V>