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9f67c9b0e7
Based on feedback from @marshallpierce that mornings took about 2.5 hours, this adjusts a bunch of the morning times downward to try to match that. In other words, this is trying to make the times in the course more accurate, rather than reducing the amount of time available for these slides. This also updates the `course-schedule` tool to be able to show per-segment timings.
51 lines
1.4 KiB
Markdown
51 lines
1.4 KiB
Markdown
---
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minutes: 5
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---
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# `Iterator`
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The [`Iterator`][1] trait supports iterating over values in a collection. It
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requires a `next` method and provides lots of methods. Many standard library
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types implement `Iterator`, and you can implement it yourself, too:
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```rust,editable
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struct Fibonacci {
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curr: u32,
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next: u32,
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}
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impl Iterator for Fibonacci {
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type Item = u32;
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fn next(&mut self) -> Option<Self::Item> {
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let new_next = self.curr + self.next;
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self.curr = self.next;
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self.next = new_next;
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Some(self.curr)
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}
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}
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fn main() {
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let fib = Fibonacci { curr: 0, next: 1 };
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for (i, n) in fib.enumerate().take(5) {
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println!("fib({i}): {n}");
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}
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}
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```
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<details>
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- The `Iterator` trait implements many common functional programming operations
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over collections (e.g. `map`, `filter`, `reduce`, etc). This is the trait
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where you can find all the documentation about them. In Rust these functions
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should produce the code as efficient as equivalent imperative implementations.
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- `IntoIterator` is the trait that makes for loops work. It is implemented by
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collection types such as `Vec<T>` and references to them such as `&Vec<T>` and
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`&[T]`. Ranges also implement it. This is why you can iterate over a vector
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with `for i in some_vec { .. }` but `some_vec.next()` doesn't exist.
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</details>
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[1]: https://doc.rust-lang.org/std/iter/trait.Iterator.html
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