memoize functions with Hashable domain

Stream: lean4

[James Gallicchio]

is there an implementation of a memoize function for arbitrary Hashable-domain functions? presumably with Std.HashMap as the backing. I'd prefer a version implemented within a StateT if the alternative is a global IO.Ref accessed unsafely or something :)

[James Gallicchio]

I see docs4#memoFix but it does not seem like what I want