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Add basic closure example

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This commit is contained in:
Timothy Warren 2019-02-01 14:50:18 -05:00
parent a05a4eb790
commit 4015bdac47
5 changed files with 116 additions and 51 deletions
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1
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@ -21,6 +21,7 @@
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5
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@ -82,8 +82,13 @@
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83
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<find>ftoc</find>
<find>expensive_closure(intensity)</find>
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<replace>expensive_result.value(intensity)</replace>
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@ -97,6 +81,7 @@
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@ -216,13 +190,13 @@
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@ -275,11 +249,11 @@
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7
closures/Cargo.toml Normal file
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@ -0,0 +1,7 @@
[package]
name = "closures"
version = "0.1.0"
authors = ["Timothy Warren <twarren@nabancard.com>"]
edition = "2018"
[dependencies]

71
closures/src/main.rs Normal file
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@ -0,0 +1,71 @@
use std::thread;
use std::time::Duration;
// @TODO: use a hashmap to memoize based on teh argument passed
// @TODO: make more generic, to accept different types of arguments
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_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)
);
}
}
}
fn main() {
let simulated_user_specified_value = 10;
let simulated_random_number = 7;
generate_workout(
simulated_user_specified_value,
simulated_random_number
);
}