Rust: What is the difference between iter and iter_mut?

iter — immutable reference. iter_mut — mutable reference.

iter:

• Immutable references.
• Cannot modify.
• Multiple iterators.

iter_mut:

• Mutable references.
• Can modify.
• Exclusive access.

1let mut v = vec![1, 2, 3];
2
3for item in v.iter() {
4    println!("{}", item);  // Read only
5}
6
7for item in v.iter_mut() {
8    *item *= 2;  // Modify
9}

Key: iter for reading, iter_mut for writing.