some iterator tuning

[rust-101.git] / workspace / src / part04.rs

diff --git a/workspace/src/part04.rs b/workspace/src/part04.rs
index fb23f2906001b0f8111df9f0a4c45b8f4315b8a7..bde913f20cf6b7750591c0bc3849daaaa09ea250 100644 (file)
--- a/workspace/src/part04.rs
+++ b/workspace/src/part04.rs
@@ -1,5 +1,3 @@
-// ***Remember to enable/add this part in `main.rs`!***
-
 // Rust-101, Part 04: Ownership, Borrowing
 // =======================================
 
@@ -16,7 +14,7 @@ fn work_on_vector(v: Vec<i32>) { /* do something */ }
 fn ownership_demo() {
     let v = vec![1,2,3,4];
     work_on_vector(v);
-    /* println!("The first element is: {}", v[0]); */
+    /* println!("The first element is: {}", v[0]); */               /* BAD! */
 }
 
 // ## Shared borrowing
@@ -25,7 +23,9 @@ fn vec_min(v: &Vec<i32>) -> Option<i32> {
     use std::cmp;
 
     let mut min = None;
-    for e in v {
+    // This time, we explicitly request an iterator for the vector `v`. The method `iter` borrows the vector
+    // it works on, and provides shared borrows of the elements.
+    for e in v.iter() {
         // In the loop, `e` now has type `&i32`, so we have to dereference it to obtain an `i32`.
         min = Some(match min {
             None => *e,
@@ -47,7 +47,7 @@ fn shared_borrow_demo() {
 // ## Mutable borrowing
 
 fn vec_inc(v: &mut Vec<i32>) {
-    for e in v {
+    for e in v.iter_mut() {
         *e += 1;
     }
 }
@@ -57,7 +57,7 @@ fn mutable_borrow_demo() {
     /* let first = &v[0]; */
     vec_inc(&mut v);
     vec_inc(&mut v);
-    /* println!("The first element is: {}", *first); */
+    /* println!("The first element is: {}", *first); */             /* BAD! */
 }
 
 // ## Summary