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Improve readability for stream::map with named struct #1

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Improve readability for stream::map with named struct #1

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13 changes: 10 additions & 3 deletions src/stream.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -30,10 +30,17 @@ pub fn map<St, U, F>(stream: St, f: F) -> impl Stream<Item = U>
where St: Stream,
F: FnMut(St::Item) -> U,
{
// stream::unfold accepts the initial state and a closure accepting the state
// the closure returns Future(None) as a terminate value
// to produce a value for the stream the closure returns Future( Some(value, state) )

// So State is a named struct to be destructured in the closure arg to improve readability
struct State<St, F> { stream: Pin<Box<St>>, f: F }

let stream = Box::pin(stream);
futures::stream::unfold((stream, f), async move | (mut stream, mut f)| {
let item = await!(next(&mut stream));
item.map(|item| (f(item), (stream, f)))
futures::stream::unfold(State { stream, f }, async move |State { mut stream, mut f }| {
let item : Option<St::Item> = await!(next(&mut stream));
item.map(|item| (f(item), State { stream, f }))
})
}

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