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48 lines
799 B
48 lines
799 B
3 years ago
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struct Cacher<T>
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where
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T: Fn(u32) -> u32,
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{
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calculation: T,
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value: Option<u32>,
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}
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impl<T> Cacher<T>
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where
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T: Fn(u32) -> u32,
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{
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fn new(calculation: T) -> Cacher<T> {
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Cacher {
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calculation,
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value: None,
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}
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}
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fn value(&mut self, arg: u32) -> u32 {
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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.calculation)(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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#[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 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, 2);
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}
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// ANCHOR_END: here
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}
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