From bb5e6272f4705c9cac65f66ca89f56558d33e08f Mon Sep 17 00:00:00 2001
From: Yuval Adam <_@yuv.al>
Date: Tue, 5 Jul 2022 19:53:39 +0300
Subject: Explicitly implement NumberSource

---
 README.md   |  1 +
 src/main.rs | 17 +++++++++++++++--
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/README.md b/README.md
index 6d1d8d4..3a5a9b1 100644
--- a/README.md
+++ b/README.md
@@ -20,6 +20,7 @@ https://github.com/tokio-rs/async-stream
 
 This page has a good review https://blog.yoshuawuyts.com/rust-streams/
 
+More good stuff at https://www.qovery.com/blog/a-guided-tour-of-streams-in-rust
 
 ## Design
 
diff --git a/src/main.rs b/src/main.rs
index 54e8529..2c31bd9 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -36,7 +36,19 @@ fn number_source() -> impl Stream<Item = u8> {
     }
 }
 
-fn double<S: Stream<Item = u8>>(input: S) -> impl Stream<Item = u8> {
+struct NumberSource {
+    i: u32,
+}
+
+impl Stream for NumberSource {
+    type Item = u32;
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        self.i += 1;
+        Poll::Ready(Some(self.i))
+    }
+}
+
+fn double<S: Stream<Item = u32>>(input: S) -> impl Stream<Item = u32> {
     stream! {
         for await val in input {
             yield val * 2
@@ -46,7 +58,8 @@ fn double<S: Stream<Item = u8>>(input: S) -> impl Stream<Item = u8> {
 
 #[tokio::main]
 async fn main() {
-    let s = double(number_source());
+    let number_source = NumberSource { i: 0 };
+    let s = double(number_source);
     pin_mut!(s); // needed for iteration
 
     while let Some(value) = s.next().await {
-- 
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