Function index_utils::merge_sparse_indices_intersect

pub fn merge_sparse_indices_intersect<I: Ord, T, U>(
    left: impl Iterator<Item = (I, T)>, 
    right: impl Iterator<Item = (I, T)>, 
    operation: impl Fn(T, T) -> U, 
    is_not_default: impl Fn(&U) -> bool
) -> Vec<(I, U)>

Collect two sparse iterators by merging the indices that they share, dropping the others.

Arguments

• left: The first iterator, sorted by index.
• right: The second iterator, sorted by index.
• operation: A binary operation applied when an element is found at some index in both iterators.
• is_not_default: A function specifying whether the result if the binary operation is the default value (that is often zero).

Return value

A vector with sparse elements by sorted and unique index.