finish parts 12, 13

[rust-101.git] / src / part06.rs

diff --git a/src/part06.rs b/src/part06.rs
index 35cd5a9dc0a82b8a35daf9618ad7498dca0d6937..6d50c2d0efcd21c64d501a7428d6c6b596756556 100644 (file)
--- a/src/part06.rs
+++ b/src/part06.rs
@@ -26,9 +26,9 @@ impl BigInt {
 }
 
 // Now we can write `vec_min`.
 }
 
 // Now we can write `vec_min`.

-//@ However, in order to make it type-check, we have to make a full (deep) copy of e by calling `clone()`.

 fn vec_min(v: &Vec<BigInt>) -> Option<BigInt> {
     let mut min: Option<BigInt> = None;
 fn vec_min(v: &Vec<BigInt>) -> Option<BigInt> {
     let mut min: Option<BigInt> = None;

+    // If `v` is a shared borrowed vector, then the default for iterating over it is to call `iter`, the iterator that borrows the elements.

     for e in v {
         let e = e.clone();                                          /*@*/
         min = Some(match min {                                      /*@*/
     for e in v {
         let e = e.clone();                                          /*@*/
         min = Some(match min {                                      /*@*/


@@ -38,7 +38,7 @@ fn vec_min(v: &Vec<BigInt>) -> Option<BigInt> {
     }
     min
 }
     }
     min
 }

-//@ Now, what's happening here? Why do we have to clone `e`, and why did we not
+//@ Now, what's happening here? Why do we have to to make a full (deep) copy of `e`, and why did we not

 //@ have to do that in our previous version?
 //@ 
 //@ The answer is already hidden in the type of `vec_min`: `v` is just borrowed, but
 //@ have to do that in our previous version?
 //@ 
 //@ The answer is already hidden in the type of `vec_min`: `v` is just borrowed, but


@@ -48,8 +48,8 @@ fn vec_min(v: &Vec<BigInt>) -> Option<BigInt> {
 //@ `e.clone()`, Rust will complain "Cannot move out of borrowed content". That's because
 //@ `e` is a `&BigInt`. Assigning `min = Some(*e)` works just like a function call: Ownership of the
 //@ underlying data is transferred from where `e` borrows from to `min`. But that's not allowed, since
 //@ `e.clone()`, Rust will complain "Cannot move out of borrowed content". That's because
 //@ `e` is a `&BigInt`. Assigning `min = Some(*e)` works just like a function call: Ownership of the
 //@ underlying data is transferred from where `e` borrows from to `min`. But that's not allowed, since

-//@ we just borrowed `e`, so we cannot empty it! We can, however, call `clone()` on it. Then we own
-//@ the copy that was created, and hence we can store it in `min`.<br/>
+//@ we just borrowed `e`, so we cannot empty it! We can, however, call `clone` on it. Then we own
+//@ the copy that was created, and hence we can store it in `min`. <br/>

 //@ Of course, making such a full copy is expensive, so we'd like to avoid it. We'll some to that in the next part.
 
 // ## `Copy` types
 //@ Of course, making such a full copy is expensive, so we'd like to avoid it. We'll some to that in the next part.
 
 // ## `Copy` types


@@ -78,7 +78,7 @@ impl<T: Copy> Copy for SomethingOrNothing<T> {}
 
 //@ ## An operational perspective
 //@ Instead of looking at what happens "at the surface" (i.e., visible in Rust), one can also explain
 
 //@ ## An operational perspective
 //@ Instead of looking at what happens "at the surface" (i.e., visible in Rust), one can also explain

-//@ ownership passing and how `Copy` and `Clone` fit in by looking at what happens on the machine.<br/>
+//@ ownership passing and how `Copy` and `Clone` fit in by looking at what happens on the machine. <br/>

 //@ When Rust code is executed, passing a value (like `i32` or `Vec<i32>`) to a function will always
 //@ result in a shallow copy being performed: Rust just copies the bytes representing that value, and
 //@ considers itself done. That's just like the default copy constructor in C++. Rust, however, will
 //@ When Rust code is executed, passing a value (like `i32` or `Vec<i32>`) to a function will always
 //@ result in a shallow copy being performed: Rust just copies the bytes representing that value, and
 //@ considers itself done. That's just like the default copy constructor in C++. Rust, however, will


@@ -92,7 +92,7 @@ impl<T: Copy> Copy for SomethingOrNothing<T> {}
 //@ `Clone`. This makes the cost explicit.
 
 // ## Lifetimes
 //@ `Clone`. This makes the cost explicit.
 
 // ## Lifetimes

-//@ To fix the performance problems of `vec_min`, we need to avoid using `clone()`. We'd like
+//@ To fix the performance problems of `vec_min`, we need to avoid using `clone`. We'd like

 //@ the return value to not be owned (remember that this was the source of our need for cloning), but *borrowed*.
 
 //@ The function `head` demonstrates how that could work: It borrows the first element of a vector if it is non-empty.
 //@ the return value to not be owned (remember that this was the source of our need for cloning), but *borrowed*.
 
 //@ The function `head` demonstrates how that could work: It borrows the first element of a vector if it is non-empty.