Attribute macro for memoizing functions using a map.
use memoize_macro::memoize;
use std::collections::{BTreeMap, HashMap};
#[memoize] // uses hashmap by default
fn fib_default(n: u64) -> u64 {
match n {
0 | 1 => 1,
n => fib_default(n - 2) + fib_default(n - 1),
}
}
#[memoize(HashMap)]
fn fib_hash(n: u64) -> u64 {
match n {
0 | 1 => 1,
n => fib_hash(n - 2) + fib_hash(n - 1),
}
}
#[memoize(BTreeMap)]
fn fib_btree(n: u64) -> u64 {
match n {
0 | 1 => 1,
n => fib_btree(n - 2) + fib_btree(n - 1),
}
}Both the function's parameters' types and the return type must be Clone.
Each choice of map might impose additional requirements (e.g. Hash + Eq for HashMap and Ord for BTreeMap).
You can use other data structures, as long as they offer get and insert methods with the same signature as the ones in the std maps.