Rust: What is the difference between truncate and clear?

truncate — keep first N. clear — remove all.

truncate:

• Keep first N.
• Drop rest.
• In-place.

clear:

• Remove all.
• Drop elements.
• Keep capacity.

1let mut v = vec![1, 2, 3, 4, 5];
2v.truncate(3);
3// v: [1, 2, 3]
4
5let mut v = vec![1, 2, 3, 4, 5];
6v.clear();
7// v: [], capacity preserved

Key: truncate for partial, clear for complete.