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<p>I think it is making progress. It's not just an engineering
milestone but also messaging. Right now a huge issue that every
Haskeller faces is new GHCs having new major versions of base. If
we make clear that "it's not base's fault, it's Template Haskell's
fault", then we will have an easier time coordinating people and
eventually fundraising to get issued fixed with Template Haskell.</p>
John
<p></p>
<div class="moz-cite-prefix">On 10/20/23 03:56, Arnaud Spiwack
wrote:<br>
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<div>A very large proportion of libraries, and virtually all
end-user applications, transitively depend on Template
Haskell. Whether they use Template Haskell directly or not. So
if we're saying “base is reinstallable, except when you have
Template Haskell somewhere”, we're effectively saying “base is
not reinstallable”. Now, it could be a good stepping-stone,
from an engineering standpoint, but I don't think we could
deliver this and be satisfied that we've accomplished
anything.<br>
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<div dir="ltr" class="gmail_attr">On Thu, 19 Oct 2023 at 13:47,
Oleg Grenrus <<a href="mailto:oleg.grenrus@iki.fi"
moz-do-not-send="true" class="moz-txt-link-freetext">oleg.grenrus@iki.fi</a>>
wrote:<br>
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<blockquote class="gmail_quote"
style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">For
what it worth, `template-haskell` itself depends on a `base`.
So if <br>
`base` if different base is used, different `template-haskell`
is to be <br>
used.<br>
<br>
In my opinion is not *too unfair* to require that if you
actually splice <br>
in (i.e. the code not only provides template-haskell
combinators to <br>
create/modify splices) then you must have base and
template-haskell <br>
versions aligned with host GHC used versions.<br>
<br>
The same restriction is GHC plugins, isn't it, except
`template-haskell` <br>
is replaced with `ghc`?<br>
<br>
- Oleg<br>
<br>
On 17.10.2023 18.54, Adam Gundry wrote:<br>
> Hi Simon,<br>
><br>
> Thanks for starting this discussion, it would be good to
see progress <br>
> in this direction. As it happens I was discussing this
question with <br>
> Ben and Matt over dinner last night, and unfortunately
they explained <br>
> to me that it is more difficult than I naively hoped,
even once <br>
> wired-in and known-key things are moved to ghc-internal.<br>
><br>
> The difficulty is that, as a normal Haskell library, ghc
itself will <br>
> be compiled against a particular version of base. Then
when Template <br>
> Haskell is used (with the internal interpreter), code
will be <br>
> dynamically loaded into a process that already has
symbols for ghc's <br>
> version of base, which means it is not safe for the code
to depend on <br>
> a different version of base. This is rather like the
situation with TH <br>
> and cross-compilers.<br>
><br>
> Adam<br>
><br>
><br>
><br>
> On 17/10/2023 11:08, Simon Peyton Jones wrote:<br>
>> Dear GHC devs<br>
>><br>
>> Given the now-agreed split between ghc-internal and
base <br>
>> <<a
href="https://github.com/haskellfoundation/tech-proposals/pull/51"
rel="noreferrer" target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://github.com/haskellfoundation/tech-proposals/pull/51</a>>,
what <br>
>> stands in the way of a "reinstallable base"?<br>
>><br>
>> Specifically, suppose that<br>
>><br>
>> * GHC 9.8 comes out with base-4.9<br>
>> * The CLC decides to make some change to `base`, so
we get base-4.10<br>
>> * Then GHC 9.10 comes out with base-4.10<br>
>><br>
>> I think we'd all like it if someone could use GHC
9.10 to compile a <br>
>> library L that depends on base-4.9 and either L
doesn't work at all <br>
>> with base-4.10, or L's dependency bounds have not yet
been adjusted <br>
>> to allow base-4.10.<br>
>><br>
>> We'd like to have a version of `base`, say
`base-4.9.1` that has the <br>
>> exact same API as `base-4.9` but works with GHC 9.10.<br>
>><br>
>> Today, GHC 9.10 comes with a specific version of
base, /and you can't <br>
>> change it/. The original reason for that was, I
recall, that GHC <br>
>> knows the precise place where (say) the type Int is
declared, and <br>
>> it'll get very confused if that data type definition
moves around.<br>
>><br>
>> But now we have `ghc-internal`, all these "things
that GHC magically <br>
>> knows" are in `ghc-internal`, not `base`.<br>
>><br>
>> *Hence my question: what (now) stops us making `base`
behave like any <br>
>> other library*? That would be a big step forward,
because it would <br>
>> mean that a newer GHC could compile old libraries
against their old <br>
>> dependencies.<br>
>><br>
>> (Some changes would still be difficult. If, for
example, we removed <br>
>> Monad and replaced it with classes Mo1 and Mo2, it
might be hard to <br>
>> simulate the old `base` with a shim. But getting 99%
of the way <br>
>> there would still be fantastic.)<br>
>><br>
>> Simon<br>
><br>
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<br>
<span class="gmail_signature_prefix">-- </span><br>
<div dir="ltr" class="gmail_signature">
<div dir="ltr">Arnaud Spiwack<br>
Director, Research at <a href="https://moduscreate.com"
rel="noopener noreferrer" target="_blank"
moz-do-not-send="true" class="moz-txt-link-freetext">https://moduscreate.com</a>
and <a href="https://tweag.io" rel="noopener noreferrer"
target="_blank" moz-do-not-send="true"
class="moz-txt-link-freetext">https://tweag.io</a>.</div>
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