[Haskell-cafe] Pointer equality for nullary constructors

[Branimir Maksimovic]

Hm, isn't that exceptions are exceptional?


On 22.02.2018. 05:21, David Feuer wrote:
> Because sometimes the sanctioned way is inefficient. throwIO always
> wraps its exception argument in a SomeException constructor before
> calling raiseIO# on the result. That extra baggage is likely enough to
> make the implementation I'm considering too slow to bother with, so I
> care right now in 2018. I'd very much prefer to get an
> officially-approved way to do what I want, but barring that I'll take
> one that works.
>
> On Wed, Feb 21, 2018 at 9:33 AM, Doug McIlroy <doug at cs.dartmouth.edu> wrote:
>>>> 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?
>>
>> Doug
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