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- use std::thread;
- use std::time::Duration;
- struct Cacher<T>
- where T: Fn(u32) -> u32
- {
- calculation: T,
- value: Option<u32>,
- }
- impl<T> Cacher<T>
- where T: Fn(u32) -> u32
- {
- fn new(calculation: T) -> Cacher<T> {
- Cacher {
- calculation,
- value: None,
- }
- }
- fn calculation(&self, num : u32) -> u32{
- println!("calculating slowly...");
- thread::sleep(Duration::from_secs(2));
- num
- }
- fn value(&mut self, arg: u32) -> u32 {
- match self.value {
- Some(v) => v,
- None => {
- let v = self.calculation(arg);
- self.value = Some(v);
- v
- },
- }
- }
- }
- fn main() {
- let simulated_user_specified_value = 50;
- let simulated_random_number = 7;
- generate_workout(
- simulated_user_specified_value,
- simulated_random_number
- );
- }
- fn generate_workout(intensity: u32, random_number: u32) {
- let mut expensive_result = Cacher::new(|num| {
- println!("calculating slowly...");
- thread::sleep(Duration::from_secs(2));
- num
- });
- if intensity < 25 {
- println!(
- "Today, do {} pushups!",
- expensive_result.value(intensity)
- );
- println!(
- "Next, do {} situps!",
- expensive_result.value(intensity)
- );
- } else {
- if random_number == 3 {
- println!("Take a break today! Remember to stay hydrated!");
- } else {
- println!(
- "Today, run for {} minutes!",
- expensive_result.value(intensity)
- );
- }
- }
- }
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