[Haskell-cafe] Pointer equality for nullary constructors

Doug McIlroy doug at cs.dartmouth.edu
Wed Feb 21 14:33:01 UTC 2018

> > Can I use reallyUnsafePtrEquality# reliably to identify whether a value is
> a nullary constructor of a particular type? 

Can this "optimization" possibly save enough time to justify
nonstandard trickery? 
This kind of obscure brittle coding may have been OK 50 years
ago. But why do it now?


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