Understanding Lifetime in Rust

When learning Rust, the first time one encounters a compilation error that states about lifetimes, can be a confusing experience.

The first thing to understand about lifetimes is that it provides yet another level of security to our program.

As we all know and probably do, sharing references is a lot better than passing data by copying their values.

Though, references are easily out of scope when not considered carefully.

So for instance

let mut r: &Vec< …

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