Go (golang) modular function cache

memo.go

/*  memoization outside of the function being memoized
    The value of this pattern is the modularity of the memoization.
    This means that if we change it from a Go map to an external
    DB store, then it's just the memo function that needs editing.
    
    Does NOT work with recursive functions.
*/

type FnInt_Int func(int) int

func memo(fn FnInt_Int) FnInt_Int {
	// if fn receives multiple args, then recommend a map of string -> result
	// and then key = Sprintf("%v %v %v", arg1, arg2, arg3)
	m := map[int]int{}

	return func(arg int) int {
		if val, ok := m[arg]; ok {
			fmt.Println("res from memo:", arg, "->", val)
			return val
		}

		res := fn(arg)
		m[arg] = res
		fmt.Println("calc & store in memo:", arg, "->", res)
		return res
	}
}

func DemoFnAddOne(n int) int { return n + 1 }

func main() {
	memDFAO := memo(DemoFnAddOne)
	fmt.Println("memDFAO 1", memDFAO(1))
	fmt.Println("memDFAO 2", memDFAO(2))
	fmt.Println("memDFAO 1", memDFAO(1))
}

/*  output:
        calc & store in memo: 1 -> 2
        memDFAO 1 2
        calc & store in memo: 2 -> 3
        memDFAO 2 3
        res from memo: 1 -> 2
        memDFAO 1 2
*/