Created
April 16, 2020 16:34
-
-
Save tstelzer/e391093533abba1afd1e5efeea81c5ab to your computer and use it in GitHub Desktop.
Rust Closures Cache
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
struct Cacher<T> | |
where | |
T: Fn(u32) -> u32, | |
{ | |
calculation: T, | |
value: HashMap<u32, u32>, | |
} | |
impl<T> Cacher<T> | |
where | |
T: Fn(u32) -> u32, | |
{ | |
fn new(calculation: T) -> Cacher<T> { | |
Cacher { | |
calculation, | |
value: HashMap::new(), | |
} | |
} | |
fn value(&mut self, arg: u32) -> u32 { | |
// FIXME: Getting a clippy warning here, recommending | |
// `self.value.entry().or_insert` instead. | |
if self.value.contains_key(&arg) { | |
*self.value.get(&arg).unwrap() | |
} else { | |
self.value.insert(arg, (self.calculation)(arg)); | |
*self.value.get(&arg).unwrap() | |
} | |
} | |
} | |
fn generate_workout(intensity: u32, random_number: u32) { | |
let mut expensive_resultexpensive_result = Cacher::new(|num| { | |
println!("calculating ..."); | |
thread::sleep(Duration::from_secs(2)); | |
num | |
}); | |
if intensity < 25 { | |
println!( | |
"Today, do {} pushups!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
println!( | |
"Next, do {} situps!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
} else if random_number == 3 { | |
println!("Take a break today! Remember to stay hydrated!"); | |
} else { | |
println!( | |
"Today, run for {} minutes!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
} | |
} | |
fn main() { | |
let simulated_user_specified_value = 10; | |
let simulated_random_number = 7; | |
generate_workout(simulated_user_specified_value, simulated_random_number); | |
} |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
struct Cacher<T> | |
where | |
T: Fn(u32) -> u32, | |
{ | |
calculation: T, | |
value: HashMap<u32, u32>, | |
} | |
impl<T> Cacher<T> | |
where | |
T: Fn(u32) -> u32, | |
{ | |
fn new(calculation: T) -> Cacher<T> { | |
Cacher { | |
calculation, | |
value: HashMap::new(), | |
} | |
} | |
fn value(&mut self, arg: u32) -> u32 { | |
let f = || (self.calculation)(arg); | |
// FIXME | |
// [rustc E0502] [E] cannot borrow `self.value` as mutable because it is also borrowed as | |
// immutable | |
// | |
// mutable borrow occurs here | |
*self.value.entry(arg).or_insert_with(f) | |
} | |
} | |
fn generate_workout(intensity: u32, random_number: u32) { | |
let mut expensive_resultexpensive_result = Cacher::new(|num| { | |
println!("calculating ..."); | |
thread::sleep(Duration::from_secs(2)); | |
num | |
}); | |
if intensity < 25 { | |
println!( | |
"Today, do {} pushups!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
println!( | |
"Next, do {} situps!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
} else if random_number == 3 { | |
println!("Take a break today! Remember to stay hydrated!"); | |
} else { | |
println!( | |
"Today, run for {} minutes!", | |
expensive_resultexpensive_result.value(intensity) | |
); | |
} | |
} | |
fn main() { | |
let simulated_user_specified_value = 10; | |
let simulated_random_number = 7; | |
generate_workout(simulated_user_specified_value, simulated_random_number); | |
} |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment