Data duplication is a tool which can be used to avoid large classes of bugs, but there's no question it comes at a cost to performance.
If anything, I would say explicit mutability allows us to decrease data duplication. By being explicit about what's mutable and what's not we don't have to resort to holding "safe copies" to ensure shared memory is not being mutated unexpectedly.
If anything, I would say explicit mutability allows us to decrease data duplication. By being explicit about what's mutable and what's not we don't have to resort to holding "safe copies" to ensure shared memory is not being mutated unexpectedly.