Struct Cacher

pub struct Cacher<F, U, V>
where
    F: Fn(U) -> V,
    U: Eq + Hash + Copy,
    V: Copy,
{ /* private fields */ }

The Cacher struct (Memoization) stores a function and a Hashmap. The HashMap keeps track of previous input and output for the function so that it only ever has to be called once per input. Use for expensive functions.

Implementations

impl<F, U, V> Cacher<F, U, V>

where F: Fn(U) -> V, U: Eq + Hash + Copy, V: Copy,

pub fn new(calculation: F) -> Cacher<F, U, V>

Constuctor for the Casher

Examples

let mut squared = Cacher::new(|n: u32| n*n);

pub fn call(&mut self, arg: U) -> V

Performs a lookup into the HashMap to see if the value has already been calculated. If it has, returns the value. If it has not, calls the function, stores the value, then returns the value.

Examples

let mut squared = Cacher::new(|n: u32| n*n);

// This is where we call the function
let sixteen = squared.call(4);

pub fn call_and_replace(&mut self, arg: U) -> V

Calls the function without performing a lookup and replaces the old return value with the new one, and returns it. Potentially useful if the function reads from a file or RNG whose state may have changed.