51 lines
874 B
Markdown
51 lines
874 B
Markdown
# Closure
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下面代码是Rust圣经课程中[闭包](http://course.rs/advance/functional-programing/closure.html#结构体中的闭包)章节的课内练习题答案：
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```rust
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struct Cacher<T,E>
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where
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T: Fn(E) -> E,
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E: Copy
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{
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query: T,
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value: Option<E>,
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}
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impl<T,E> Cacher<T,E>
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where
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T: Fn(E) -> E,
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E: Copy
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{
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fn new(query: T) -> Cacher<T,E> {
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Cacher {
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query,
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value: None,
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}
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}
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fn value(&mut self, arg: E) -> E {
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match self.value {
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Some(v) => v,
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None => {
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let v = (self.query)(arg);
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self.value = Some(v);
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v
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}
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}
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}
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}
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fn main() {
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}
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#[test]
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fn call_with_different_values() {
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let mut c = Cacher::new(|a| a);
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let v1 = c.value(1);
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let v2 = c.value(2);
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assert_eq!(v2, 1);
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}
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``` |