[Haskell-cafe] Pointer equality for nullary constructors

[David Feuer]

Well, not always. They have special support in the RTS that seems worth
experimenting with. setjmp/longjmp is what I'm after.

On Feb 21, 2018 11:24 PM, "Branimir Maksimovic" <
branimir.maksimovic at gmail.com> wrote:

> 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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