mirror of https://github.com/rust-lang/book
42 lines
802 B
Rust
42 lines
802 B
Rust
struct Counter {
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count: u32,
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}
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impl Counter {
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fn new() -> Counter {
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Counter { count: 0 }
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}
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}
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impl Iterator for Counter {
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type Item = u32;
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fn next(&mut self) -> Option<Self::Item> {
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if self.count < 5 {
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self.count += 1;
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Some(self.count)
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} else {
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None
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}
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}
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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// ANCHOR: here
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#[test]
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fn calling_next_directly() {
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let mut counter = Counter::new();
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assert_eq!(counter.next(), Some(1));
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assert_eq!(counter.next(), Some(2));
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assert_eq!(counter.next(), Some(3));
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assert_eq!(counter.next(), Some(4));
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assert_eq!(counter.next(), Some(5));
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assert_eq!(counter.next(), None);
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}
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// ANCHOR_END: here
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}
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