[Haskell-cafe] Efficient object identity (aka symbols as data)

[Brandon Allbery]

On Thu, May 26, 2011 at 04:45, Jacek Generowicz <jacek.generowicz at cern.ch>wrote:

> What is the Haskell approach to efficient comparison and lookup of objects
> by their identity?
>

ghc uses Data.Unique to generate unique internal identifiers to associate
with things.  (Think gensym.  Hm, except last time I did anything serious
with Lisp, it was Maclisp... does gensym even still exist, or did CL do
something inscrutable with it?)  Beyond that, the existence of functions
such as reallyUnsafePointerEquality# makes me think it's a Hard Problem.
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