Function memorizeAfterN

memorizeAfterN<K, V>(
    n: number,
    fn: (arg: K) => V,
    default_value?: V,
): (arg: K) => V

memorizes a function's return value up-until n-calls, and after this, unmemorized call arguments will either return the optional default_value (if it was provided), or it will return value of the nth call (final call that got memorized).

Type Parameters

Parameters

n: number
fn: (arg: K) => V
Optionaldefault_value: V

Returns (arg: K) => V

Example

import { assertEquals as assertEq } from "jsr:@std/assert"

let fn_call_count = 0
const fn = (arg: string | number) => {
	fn_call_count++
	return `you owe ${arg} to the bank.`
}
const memorized_fn = memorizeAfterN(2, fn, "DEFAULT VALUE!")

assertEq(memorized_fn("a camel")  , "you owe a camel to the bank.")
assertEq(fn_call_count            , 1)
assertEq(memorized_fn("a camel")  , "you owe a camel to the bank.")
assertEq(fn_call_count            , 1)
assertEq(memorized_fn("5")        , "you owe 5 to the bank.")
assertEq(fn_call_count            , 2)
// from here on, memorization will be halted and only `"DEFAULT VALUE!"` will be returned for unmemorized args
assertEq(memorized_fn("5")        , "you owe 5 to the bank.")
assertEq(fn_call_count            , 2)
assertEq(memorized_fn(5)          , "DEFAULT VALUE!")
assertEq(fn_call_count            , 2)
assertEq(memorized_fn("your soul"), "DEFAULT VALUE!")
assertEq(fn_call_count            , 2)
assertEq(memorized_fn("your soul"), "DEFAULT VALUE!")
assertEq(fn_call_count            , 2)
assertEq(memorized_fn("a camel")  , "you owe a camel to the bank.")
assertEq(fn_call_count            , 2)