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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 value(&mut self, arg: u32) -> u32 {
match self.value {
Some(v) => v,
None => {
let v = (self.calculation)(arg);
self.value = Some(v);
v
}
}
}
}
fn generate_work(intensity: u32, random_number: u32) {
let mut expensive_clourse = Cacher::new(|num| {
println!("calculating slowly...");
thread::sleep(Duration::from_secs(2));
num
});
if intensity < 25 {
println!("Today, do {} pushups!", expensive_clourse.value(intensity));
println!("Next, do {} situps!", expensive_clourse.value(intensity));
} else {
if random_number == 3 {
println!("Take a break today! Remember to stay hydrated!");
} else {
println!("Today, run for {} minutes!", expensive_clourse.value(intensity));
}
}
}
fn main() {
let simulated_user_specified_value = 10;
let simulated_random_number = 7;
generate_work(simulated_user_specified_value, simulated_random_number);
}
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