lecture 3 stuff

lectures/03/veciter2.rs

@@ -0,0 +1,79 @@
+// example on how to implement iterators
+struct VecIntoIter<T> {
+    v: Vec<T>,
+    len: usize,
+    i: usize,
+}
+
+impl<T> VecIntoIter<T> {
+    fn new(v: Vec<T>) -> Self {
+        Self {
+            len: v.len(),
+            v,
+            i: 0
+        }
+    }
+}
+
+struct VecIter<'a, T> {
+    v: &'a Vec<T>,
+    len: usize,
+    i: usize,
+}
+
+
+impl<'a, T> VecIter<'a, T> {
+    fn new(v: &'a Vec<T>) -> Self {
+        Self {
+            len: v.len(),
+            v,
+            i: 0
+        }
+    }
+}
+
+impl<'a, T> Iterator for VecIter<'a, T> {
+    type Item = &'a T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.i >= self.len {
+            return None;
+        }
+        let n = self.i;
+        self.i += 1;
+        Some(&self.v[n])
+    }
+}
+
+
+impl<T: Copy> Iterator for VecIntoIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.i >= self.len {
+            return None;
+        }
+        let n = self.i;
+        self.i += 1;
+        Some(self.v[n])
+    }
+}
+
+fn main() {
+    let v = vec![1, 2, 3];
+
+    let mut it = VecIter::new(&v);
+
+    while let Some(x) = it.next() {
+        println!("{x}");
+    }
+
+    println!("{v:?}");
+ 
+    let mut it = VecIntoIter::new(v);
+
+    while let Some(x) = it.next() {
+        println!("{x}");
+    }
+    // println!("{v:?}");  // v is consumed
+}