Is immutability by default worth the hassle?

32

I think this is a misuderstanding.

let x = 13;

is a hard guarantee. It guarantees that x will not change.

You can make a copy and change that, but that's not a loophole to that rule: x will still not change.

The same is true for:

let x = String::from("abc");

You have a hard guarantee: whenever you use x, it will contain "abc".

You can move the string elsewhere and change it there, but then it's no longer x that you're changing. That's not a loophole.

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