//@ `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 {
- pub data: Vec<u64>,
+ pub data: Vec<u64>, // least significant digit first, no trailing zeros
}
// Now that we fixed the data representation, we can start implementing methods on it.
//@ fields and initial values assigned to them.
pub fn new(x: u64) -> Self {
if x == 0 {
- BigInt { data: vec![] }
+ BigInt { data: vec![] } /*@*/
} else {
BigInt { data: vec![x] } /*@*/
}
//
// **Exercise 05.1**: Implement this function.
//
- // *Hint*: You can use `pop()` to remove the last element of a vector.
+ // *Hint*: You can use `pop` to remove the last element of a vector.
pub fn from_vec(mut v: Vec<u64>) -> Self {
unimplemented!()
}
//@ `#[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
-// digits? The number of non-zero digits? The smallest/largest digit?
+// digits? The number of non-zero digits? The smallest/largest digit? Of course, these should all just borrow `self`.
// ## 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