From: Martin Pitt <martin@piware.de>
Date: Thu, 26 Aug 2021 16:30:39 +0000 (+0200)
Subject: Iterators
X-Git-Url: https://piware.de/gitweb/?p=learn-rust.git;a=commitdiff_plain;h=105f3ee65d6d52bdeddda90afde8ebfcacc416e8

Iterators
---

diff --git a/src/lib.rs b/src/lib.rs
index fe3b71b..b7e5eb8 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -85,3 +85,26 @@ where
         }
     }
 }
+
+pub struct Counter5 {
+    count: u32
+}
+
+impl Counter5 {
+    pub fn new() -> Counter5 {
+        Counter5 { count: 0 }
+    }
+}
+
+impl Iterator for Counter5 {
+    type Item = u32;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.count < 5 {
+            self.count += 1;
+            Some(self.count)
+        } else {
+            None
+        }
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 3b45c88..06d122b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -157,6 +157,38 @@ fn test_closures() {
     println!("1st int call for value defg: {}", expensive_str_result.value("defg"));
 }
 
+fn test_iterators() {
+    let v1 = vec!["Hello", "good", "world"];
+    // implied default is .into_iter() which consumes v1
+    for s in v1.iter() {
+        println!("element: {}", s);
+    }
+    // can still use it now
+    println!("v1: {:?}", &v1);
+
+    // manual iteration
+    let mut v1_iter = v1.iter();
+    while let Some(e) = v1_iter.next() {
+        println!("while loop over iter: {}", e);
+    }
+
+    for l_element in v1.iter().filter(|x| x.contains('l')) {
+        println!("v1 element containing 'l': {}", l_element);
+    }
+
+    let v2 = vec![1, 2, 3];
+    let double_v2: Vec<_> = v2.iter().map(|x| x * 2).collect();
+    println!("doubled v2: {:?}", double_v2);
+
+    for i in v2.into_iter().map(|x| x * 3) {
+        println!("for loop triplicating v2: {}", i);
+    }
+
+    for i in Counter5::new() {
+        println!("Counter 5 value: {}", i);
+    }
+}
+
 fn main() {
     test_strings();
     test_vectors();
@@ -164,4 +196,5 @@ fn main() {
     test_files();
     test_generics();
     test_closures();
+    test_iterators();
 }