Method and_modify

src/entity/sparse.rs:432–440

(mut self, f: F)

    where
        F: FnOnce(&mut V),
    {
        if let Entry::Occupied(entry) = &mut self {
            f(entry.get_mut());
        }
        self
    }

    /// Inserts a default-constructed value in the entry if it is vacant and returns a mutable
    /// reference to it. Otherwise a mutable reference to an already existent value is returned.
    #[inline]
    pub fn or_default(self) -> &'a mut V
    where