Optimize by avoiding intermediate structures.

[tkaitchuck]

Often collections are used in loops where multiple updates/operations are performed at once.
If there were a way to perform multiple updates at once these could be made more efficient.

The most obvious way to do this would be to optimize this:

im-rs/src/ord/map.rs

Lines 1997 to 2001 in 3f4e01a

	let mut m = OrdMap::default();
	for (k, v) in i {
	m.insert(From::from(k), From::from(v));
	}
	m

and similar methods internally. Then for users taking advantage of the higher performance is just a matter of making better use of the existing traits.

In the above function, a new OrdMap is being constructed, and won't be seen by the caller until all the inserts are completed, yet every intermediate map is created and thrown out.

[SimonSapin]

every intermediate map is created and thrown out

Every mutating operation is based on make_mut. For example in insert:

im-rs/src/ord/map.rs

Line 744 in 3f4e01a

let root = PoolRef::make_mut(&self.pool.0, &mut self.root);

This only clones when a value is shared. When however the reference count is 1, the same value can be reused and mutated in place. So there’s not much creating and throwing out as you seem to think.