Method retain

src/entity/sparse.rs:289–298

(&mut self, mut keep: F)

    /// order.
    #[inline]
    pub fn retain<F>(&mut self, mut keep: F)
    where
        F: FnMut(K, &mut V) -> bool,
    {
        let prev_len = self.dense.len();
        self.dense.retain_mut(|&mut (k, ref mut v)| keep(k, v));
        if prev_len != self.dense.len() {
            self.rebuild_mapping();
        }
    }
}

impl<K, V> Default for SparseMap<K, V>