A comment on Introspective-Haskell

Levent Erkok erkokl at gmail.com
Fri Dec 11 22:54:36 UTC 2015

Spot on.. I really want "Template Core," independent of TH.

To be honest, "GHC Plugins" already provides "Template Core" in this sense;
but would be nicer if one can get his hands on the Core in the regular
Haskell context, not just in a plugin context. So, perhaps "Template Core"
is not the biggest priority in the big scheme of things.

On Fri, Dec 11, 2015 at 2:23 PM, Richard Eisenberg <eir at cis.upenn.edu>

> I'm seeing several different directions here, and it may be helpful to
> clarify what's going on:
> * My original proposal was about changing the implementation of Template
> Haskell in a way that casual TH users wouldn't notice (by going through the
> compatibility shim). Once this is done, it may be possible to extend the
> idea to Core, but that wasn't my primary motivation.
> * It seems that Levant wants Template Core. This idea is actually
> orthogonal from my original proposal, in that Template Core can be
> implemented with introspection or not. I think it will be easier with
> introspection, but it's just a matter of engineering either way.
> * I don't think any real movement can be made on either of these issues
> without editing GHC itself. I don't see what a purely-external library
> could do.
> * Yes yes yes, lots lots lots of pattern synonyms.
> Does this clarify anything?
> Richard
> On Dec 9, 2015, at 12:28 PM, Levent Erkok <erkokl at gmail.com> wrote:
> Thomas: I honestly don't see why TH needs to go away. The way I viewed
> Richard's proposal was a means for me to get my hands on Core-splices
> inside my regular Haskell code. I think the two can co-exist happily.
> Perhaps others can opine on why we can't have both, aside from perhaps an
> argument about added complexity of having two different kinds of splices.
> If there was an effort to allow Core-splices, I'd be happy to contribute
> so much as I can. Whether that ends up replacing TH or a compatibility shim
> is actually needed is a different question in my mind. That can be decided
> based on the experience with having Core-splices working first?
> Please correct me if I'm wrong; in that TH and Core-splices cannot
> coexist, at least in theory, for some other reason.
> -Levent.
> On Wed, Dec 9, 2015 at 7:55 AM, Thomas Bereknyei <tomberek at gmail.com>
> wrote:
>> This should be possible to start as a custom library. Appropriately
>> shimming the result back into TH. Then with some experience and lessons
>> learned we can investigate replacing TH with this new approach.
>> I ran across many similar issues with TH, haskell-src-exts,
>> haskell-src-meta, etc.
>> Levent: Would it be appropriate for us to start putting together this
>> shim? As Simon says in (
>> https://ghc.haskell.org/trac/ghc/ticket/11081#comment:5) we can go a
>> long ways with a plethora of pattern synonyms.
>> On Tue, Dec 8, 2015 at 9:51 PM, Levent Erkok <erkokl at gmail.com> wrote:
>>> I just came across https://ghc.haskell.org/trac/ghc/ticket/11081, and
>>> the corresponding wiki-page:
>>> https://ghc.haskell.org/trac/ghc/wiki/TemplateHaskell/Introspective
>>> I think this is a terrific idea. In the past, I've tried both TH and
>>> haskell-src-exts to do relatively simple things, but ended-up abandoning
>>> them due to the inherent complexity of source level haskell that had very
>>> little to do with what I really cared about. Being able to get your hands
>>> on Core at the regular Haskell level would truly simplify life, and I
>>> suspect would open the flood-gates for a lot of people to develop extremely
>>> cool/useful artifacts, making the GHC/Haskell experience even better.
>>> I hope this idea is taken further and sees the light-of-day.
>>> Richard: Did you have any further thoughts about possible plans?
>>> -Levent.
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