//@ to use a vector "digits" of the number. This is like "1337" being a vector of four digits (1, 3, 3, 7),
//@ except that we will use `u64` as type of our digits, meaning we have 2^64 individual digits. Now we just
//@ have to decide the order in which we store numbers. I decided that we will store the least significant
//@ to use a vector "digits" of the number. This is like "1337" being a vector of four digits (1, 3, 3, 7),
//@ except that we will use `u64` as type of our digits, meaning we have 2^64 individual digits. Now we just
//@ have to decide the order in which we store numbers. I decided that we will store the least significant
-//@ digit first. This means that "1337" would actually become (7, 3, 3, 1).<br/>
+//@ digit first. This means that "1337" would actually become (7, 3, 3, 1). <br/>
//@ Finally, we declare that there must not be any trailing zeros (corresponding to
//@ useless leading zeros in our usual way of writing numbers). This is to ensure that
//@ the same number can only be stored in one way.
//@ Finally, we declare that there must not be any trailing zeros (corresponding to
//@ useless leading zeros in our usual way of writing numbers). This is to ensure that
//@ the same number can only be stored in one way.
//@ `data` public - otherwise, the next parts of this course could not work on `BigInt`s. Of course, in a
//@ real program, one would make the field private to ensure that the invariant (no trailing zeros) is maintained.
pub struct BigInt {
//@ `data` public - otherwise, the next parts of this course could not work on `BigInt`s. Of course, in a
//@ real program, one would make the field private to ensure that the invariant (no trailing zeros) is maintained.
pub struct BigInt {
- // declaration for `v` here is just like the one in `let mut ...`, it says that we will locally
- // change the vector `v`.
+ // declaration for `v` here is just like the one in `let mut ...`: We completely own `v`, but Rust
+ // still asks us to make our intention of modifying it explicit. This `mut` is *not* part of the
+ // type of `from_vec` - the caller has to give up ownership of `v` anyway, so they don't care anymore
+ // what you do to it.
//@ `#[derive(Clone)]` right before the definition of `SomethingOrNothing`.
// **Exercise 05.2**: Write some more functions on `BigInt`. What about a function that returns the number of
//@ `#[derive(Clone)]` right before the definition of `SomethingOrNothing`.
// **Exercise 05.2**: Write some more functions on `BigInt`. What about a function that returns the number of
// ## Mutation + aliasing considered harmful (part 2)
//@ Now that we know how to borrow a part of an `enum` (like `v` above), there's another example for why we
// ## Mutation + aliasing considered harmful (part 2)
//@ Now that we know how to borrow a part of an `enum` (like `v` above), there's another example for why we
Variant::Number(ref mut n) => ptr = n,
Variant::Text(_) => return,
}
Variant::Number(ref mut n) => ptr = n,
Variant::Text(_) => return,
}
*ptr = 1337;
}
//@ Now, imagine what would happen if we were permitted to also mutate `var`. We could, for example,
*ptr = 1337;
}
//@ Now, imagine what would happen if we were permitted to also mutate `var`. We could, for example,