> The viewpoint I meant is the technical My objection was also a technical one: Haskell doesn't give you access to the physical identity of any runtime object

> The viewpoint I meant is the technical My objection was also a technical one: Haskell doesn't give you access to the physical identity of any runtime object that isn't a reference cell (`IORef`, `STRef`, `MVar`, `TVar`, etc.). > (and performance-centric) one The ability to pass around arbitrarily complicated values in O(1) time is an intrinsic part of Haskell's cost model. This is the most natural thing in the world, unless you've lived all your life subordinating values to object identities, in which case, yes, non-destructively transferring a value from one object identity to another (aka “deep cloning”) might be an arbitrarily expensive operation.