tune part 16

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

diff --git a/src/part06.rs b/src/part06.rs
index 5b90142825798a25321352f136b1c9c913d555a7..8161d2d1d37dc6bd70bdda7b93f9779c36919dcb 100644 (file)
--- a/src/part06.rs
+++ b/src/part06.rs
@@ -26,11 +26,11 @@ 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 {
     for e in v {

-        let e = e.clone();                                          /*@*/
+        let e = e.clone();

         min = Some(match min {                                      /*@*/
             None => e,                                              /*@*/
             Some(n) => e.min_try1(n)                                /*@*/
         min = Some(match min {                                      /*@*/
             None => e,                                              /*@*/
             Some(n) => e.min_try1(n)                                /*@*/


@@ -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


@@ -50,7 +50,7 @@ fn vec_min(v: &Vec<BigInt>) -> Option<BigInt> {
 //@ 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/>
 //@ 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/>

-//@ 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.
+//@ Of course, making such a full copy is expensive, so we'd like to avoid it. We'll come to that in the next part.

 
 // ## `Copy` types
 //@ But before we go there, I should answer the second question I brought up above: Why did our old `vec_min` work?
 
 // ## `Copy` types
 //@ But before we go there, I should answer the second question I brought up above: Why did our old `vec_min` work?