+++ /dev/null
-// Rust-101, Part 08: Associated Types, Modules
-// ============================================
-
-use std::{cmp,ops};
-use part05::BigInt;
-
-
-// So, let us write a function to "add with carry", and give it the appropriate type. Notice Rust's native support for pairs.
-fn overflowing_add(a: u64, b: u64, carry: bool) -> (u64, bool) {
- let sum = a.wrapping_add(b);
- // If an overflow happened, then the sum will be smaller than *both* summands. Without an overflow, of course, it will be
- // at least as large as both of them. So, let's just pick one and check.
- if sum >= a {
- // The addition did not overflow. <br/>
- // **Exercise 08.1**: Write the code to handle adding the carry in this case.
- unimplemented!()
- } else {
- // Otherwise, the addition *did* overflow. It is impossible for the addition of the carry
- // to overflow again, as we are just adding 0 or 1.
- unimplemented!()
- }
-}
-
-// `overflow_add` is a sufficiently intricate function that a test case is justified.
-// This should also help you to check your solution of the exercise.
-/*#[test]*/
-fn test_overflowing_add() {
- assert_eq!(overflowing_add(10, 100, false), (110, false));
- assert_eq!(overflowing_add(10, 100, true), (111, false));
- assert_eq!(overflowing_add(1 << 63, 1 << 63, false), (0, true));
- assert_eq!(overflowing_add(1 << 63, 1 << 63, true), (1, true));
- assert_eq!(overflowing_add(1 << 63, (1 << 63) -1 , true), (0, true));
-}
-
-// ## Associated Types
-impl ops::Add<BigInt> for BigInt {
-
- // Here, we choose the result type to be again `BigInt`.
- type Output = BigInt;
-
- // Now we can write the actual function performing the addition.
- fn add(self, rhs: BigInt) -> Self::Output {
- // We know that the result will be *at least* as long as the longer of the two operands,
- // so we can create a vector with sufficient capacity to avoid expensive reallocations.
- let max_len = cmp::max(self.data.len(), rhs.data.len());
- let mut result_vec:Vec<u64> = Vec::with_capacity(max_len);
- let mut carry = false; /* the current carry bit */
- for i in 0..max_len {
- let lhs_val = if i < self.data.len() { self.data[i] } else { 0 };
- let rhs_val = if i < rhs.data.len() { rhs.data[i] } else { 0 };
- // Compute next digit and carry. Then, store the digit for the result, and the carry for later.
- unimplemented!()
- }
- // **Exercise 08.2**: Handle the final `carry`, and return the sum.
- unimplemented!()
- }
-}
-
-// ## Traits and reference types
-
-// Writing this out becomes a bit tedious, because trait implementations (unlike functions) require full explicit annotation
-// of lifetimes. Make sure you understand exactly what the following definition says. Notice that we can implement a trait for
-// a reference type!
-impl<'a, 'b> ops::Add<&'a BigInt> for &'b BigInt {
- type Output = BigInt;
- fn add(self, rhs: &'a BigInt) -> Self::Output {
- // **Exercise 08.3**: Implement this function.
- unimplemented!()
- }
-}
-
-// **Exercise 08.4**: Implement the two missing combinations of arguments for `Add`. You should not have to duplicate the implementation.
-
-// ## Modules
-
-// Rust calls a bunch of definitions that are grouped together a *module*. You can put the tests in a submodule as follows.
-#[cfg(test)]
-mod tests {
- use part05::BigInt;
-
- /*#[test]*/
- fn test_add() {
- let b1 = BigInt::new(1 << 32);
- let b2 = BigInt::from_vec(vec![0, 1]);
-
- assert_eq!(&b1 + &b2, BigInt::from_vec(vec![1 << 32, 1]));
- // **Exercise 08.5**: Add some more cases to this test.
- }
-}
-
-// **Exercise 08.6**: Write a subtraction function, and testcases for it. Decide for yourself how you want to handle negative results.
-// For example, you may want to return an `Option`, to panic, or to return `0`.
-
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