1. Sheer comparison for equality is used. (It is user definable.) For e.g. built-in hashes, contents must compare equal.

2. The store is a hashtable.

3. Multiple arguments are grouped in a tuple - no major complication.

4. Where memoization doesn't make sense you'll get a compile-time error because e.g. comparison for equality is't defined. At least most of the time :o).

5. The memory is thread-local.

6. memoize takes the name of the memoized argument and creates a distinct type for each memoized function.

TL;DR: business as usual