1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96

use std::thread;
use std::time::Duration;
use std::collections::HashMap;

pub struct Cacher<T, P, O> 
	where T: Fn(P) -> O,
		  P: std::cmp::Eq + std::hash::Hash + Copy,
		  O: Copy

{
	pub caculation: T,
	pub value: HashMap<P, O>,
}
	
/// ```
/// let mut c = testclourse::Cacher::new(|a| a);
/// let v = c.value(2);
/// assert_eq!(v, 2);
/// let mut c2 = testclourse::Cacher::new(|mystring: &str| mystring.len());
/// let v2 = c2.value("abcd");
/// assert_eq!(v, 2);
/// ```
impl<T, P, O> Cacher<T, P, O>
	where T: Fn(P) -> O,
		  P: std::cmp::Eq + std::hash::Hash + Copy,
		  O: Copy
{
	pub fn new(caculation: T) -> Cacher<T, P, O> {
		Cacher {
			caculation,
			value: HashMap::new(),
		}
	}

	pub fn value(&mut self, arg: P) -> O {
		let ret = match self.value.get(&arg) {
			Some(v) => *v,
			None => {
				let v = (self.caculation)(arg);
				v
			}
		};
		self.value.insert(arg, ret);
		ret
	}

}


pub 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)
            );
        }
    }
}

#[cfg(test)]
mod test {
	use super::*;

	#[test]
	fn call_with_different_values() {
		let mut c = Cacher::new(|a| a);
		let _v1 = c.value(1);
    	let v2 = c.value(2);
		assert_eq!(v2, 2);
	}

	#[test]
	fn call_with_different_values_2() {
		let mut c = Cacher::new(|mystring: &str| mystring.len());
		let _v1 = c.value("abc");
    	let v2 = c.value("abcde");
		assert_eq!(v2, 5);
	}
}