From pjakobsen at gmail.com  Sat Aug  1 12:36:55 2015
From: pjakobsen at gmail.com (Peder Jakobsen)
Date: Sat, 1 Aug 2015 08:36:55 -0400
Subject: Newbie: Can't understand cabal errors during install of hakyll
Message-ID: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC@gmail.com>

Hi, 

Been with Haskell just for few days, and thought it would be a good exercise to run a static site generator to get familiar with various tools, and I?m already running into ?cabal hell? I think.  :(


$ cabal install hakyll
Resolving dependencies...
cabal: Could not resolve dependencies:
trying: hakyll-4.7.2.0 (user goal)
next goal: time (dependency of hakyll-4.7.2.0)
rejecting: time-1.4.2/installed-d67... (conflict: hakyll => time>=1.5 && <1.6)
trying: time-1.5.0.1
trying: process-1.2.0.0/installed-3a4... (dependency of hakyll-4.7.2.0)
next goal: unix (dependency of process-1.2.0.0/installed-3a4...)
rejecting: unix-2.7.0.1/installed-8ad... (conflict: time==1.5.0.1, unix =>
time==1.4.2/installed-d67...)
rejecting: unix-2.7.1.0, 2.7.0.1, 2.7.0.0, 2.6.0.1, 2.6.0.0, 2.5.1.1, 2.5.1.0,
2.5.0.0, 2.4.2.0, 2.4.1.0, 2.4.0.2, 2.4.0.1, 2.4.0.0, 2.3.2.0, 2.3.1.0,
2.3.0.0, 2.2.0.0, 2.0 (conflict: process => unix==2.7.0.1/installed-8ad...)
Backjump limit reached (change with --max-backjumps).


I?m running OS X Yosemite 10.2.2 with all the latest versions of  Haskell and cabal.

Thanks  you for listening. :)

Peder 
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From pjakobsen at gmail.com  Sat Aug  1 12:52:33 2015
From: pjakobsen at gmail.com (Peder Jakobsen)
Date: Sat, 1 Aug 2015 08:52:33 -0400
Subject: Uninstalling packages?
Message-ID: <DA2222C3-0683-469C-98F8-551D41EBF55E@gmail.com>

Hi, just browsed through the user guide on managing packages at at https://www.haskell.org/cabal/users-guide/installing-packages.html <https://www.haskell.org/cabal/users-guide/installing-packages.html>

Managing seems to imply that you should also be able to uninstall packages with a simple command.  But there seem to be no instructions for how to do this for an installed packaged.  What am I missing?  Is it called ?deregistering??

Thanks again, 

P.
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From adam at bergmark.nl  Sat Aug  1 13:34:58 2015
From: adam at bergmark.nl (Adam Bergmark)
Date: Sat, 1 Aug 2015 15:34:58 +0200
Subject: Newbie: Can't understand cabal errors during install of hakyll
In-Reply-To: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC@gmail.com>
References: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC@gmail.com>
Message-ID: <CACnqJZaHNhU5Y9r=v59ya4x2V-NVxoriWxMvj+_qs6G+XrO2UA@mail.gmail.com>

It seems like you have time-1.4.2 installed, the latest GHC (7.10) comes
with time 1.5.*. Are you sure you are on 7.10?

The core of the problem is that hakyll needs time >= 1.5, and unix is using
the pre-installed time-1.4.2. This is rejected because only one version of
a library can be used in the same install plan.

As the error message suggests you can you increase the backjump limit so
I'd try that first. I typically pass --reorder-goals --max-backjumps=-1 to
cabal-install. Running this sometimes takes a long time, but it will finish
eventually.

You can also try installing an older version of hakyll that works with
time-1.4.2 (see the hackage page for info on older versions).

Lastly,  are you using a sandbox? It also helps with reducing problems. I
never install anything in the global or user level package db, only in
sandboxes.

HTH,
Adam



On Sat, Aug 1, 2015 at 2:36 PM, Peder Jakobsen <pjakobsen at gmail.com> wrote:

> Hi,
>
> Been with Haskell just for few days, and thought it would be a good
> exercise to run a static site generator to get familiar with various tools,
> and I?m already running into ?cabal hell? I think.  :(
>
>
> $ cabal install hakyll
> Resolving dependencies...
> cabal: Could not resolve dependencies:
> trying: hakyll-4.7.2.0 (user goal)
> next goal: time (dependency of hakyll-4.7.2.0)
> rejecting: time-1.4.2/installed-d67... (conflict: hakyll => time>=1.5 &&
> <1.6)
> trying: time-1.5.0.1
> trying: process-1.2.0.0/installed-3a4... (dependency of hakyll-4.7.2.0)
> next goal: unix (dependency of process-1.2.0.0/installed-3a4...)
> rejecting: unix-2.7.0.1/installed-8ad... (conflict: time==1.5.0.1, unix =>
> time==1.4.2/installed-d67...)
> rejecting: unix-2.7.1.0, 2.7.0.1, 2.7.0.0, 2.6.0.1, 2.6.0.0, 2.5.1.1,
> 2.5.1.0,
> 2.5.0.0, 2.4.2.0, 2.4.1.0, 2.4.0.2, 2.4.0.1, 2.4.0.0, 2.3.2.0, 2.3.1.0,
> 2.3.0.0, 2.2.0.0, 2.0 (conflict: process => unix==2.7.0.1/installed-8ad..
> .)
> Backjump limit reached (change with --max-backjumps).
>
>
> I?m running OS X Yosemite 10.2.2 with all the latest versions of  Haskell
> and cabal.
>
> Thanks  you for listening. :)
>
> Peder
>
> _______________________________________________
> cabal-devel mailing list
> cabal-devel at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>
>
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From adam at bergmark.nl  Sat Aug  1 13:47:37 2015
From: adam at bergmark.nl (Adam Bergmark)
Date: Sat, 1 Aug 2015 15:47:37 +0200
Subject: Uninstalling packages?
In-Reply-To: <DA2222C3-0683-469C-98F8-551D41EBF55E@gmail.com>
References: <DA2222C3-0683-469C-98F8-551D41EBF55E@gmail.com>
Message-ID: <CACnqJZaRy3E9zks_oWTP_YCcgPGqUT=u_ceiEDqEGhmpvpq2sg@mail.gmail.com>

There is no uninstall command, there was at one point but it didn't do
anything ;-)

Unregistering a package does not delete any files, but it will make cabal
forget about its existence.
If you are working in a sandbox you can simply `cabal sandbox delete; cabal
sandbox init` to start from scratch, you can also deregister packages there
with `cabal sandbox hc-pkg unregister`, outside a sandbox it's `ghc-pkg
unregister`.

There are also tools on hackage that can clean up files when unregistering,
iirc cab[1] can.

HTH,
Adam

[1] http://hackage.haskell.org/package/cab


On Sat, Aug 1, 2015 at 2:52 PM, Peder Jakobsen <pjakobsen at gmail.com> wrote:

> Hi, just browsed through the user guide on managing packages at at
> https://www.haskell.org/cabal/users-guide/installing-packages.html
>
> *Managing* seems to imply that you should also be able to uninstall
> packages with a simple command.  But there seem to be no instructions for
> how to do this for an installed packaged.  What am I missing?  Is it
> called ?deregistering??
>
> Thanks again,
>
> P.
>
> _______________________________________________
> cabal-devel mailing list
> cabal-devel at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>
>
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From pjakobsen at gmail.com  Sat Aug  1 14:09:43 2015
From: pjakobsen at gmail.com (Peder Jakobsen)
Date: Sat, 1 Aug 2015 10:09:43 -0400
Subject: Uninstalling packages?
In-Reply-To: <CACnqJZaRy3E9zks_oWTP_YCcgPGqUT=u_ceiEDqEGhmpvpq2sg@mail.gmail.com>
References: <DA2222C3-0683-469C-98F8-551D41EBF55E@gmail.com>
 <CACnqJZaRy3E9zks_oWTP_YCcgPGqUT=u_ceiEDqEGhmpvpq2sg@mail.gmail.com>
Message-ID: <7B2976A4-53DE-4676-AA1F-54C3AC04E9EA@gmail.com>

Wonderful.  Thanks Adam for the quick reply, much appreciated.  :)

> On Aug 1, 2015, at 9:47 AM, Adam Bergmark <adam at bergmark.nl> wrote:
> 
> There is no uninstall command, there was at one point but it didn't do anything ;-)
> 
> Unregistering a package does not delete any files, but it will make cabal forget about its existence.
> If you are working in a sandbox you can simply `cabal sandbox delete; cabal sandbox init` to start from scratch, you can also deregister packages there with `cabal sandbox hc-pkg unregister`, outside a sandbox it's `ghc-pkg unregister`.
> 
> There are also tools on hackage that can clean up files when unregistering, iirc cab[1] can.
> 
> HTH,
> Adam
> 
> [1] http://hackage.haskell.org/package/cab <http://hackage.haskell.org/package/cab>
> 
> 
> On Sat, Aug 1, 2015 at 2:52 PM, Peder Jakobsen <pjakobsen at gmail.com <mailto:pjakobsen at gmail.com>> wrote:
> Hi, just browsed through the user guide on managing packages at at https://www.haskell.org/cabal/users-guide/installing-packages.html <https://www.haskell.org/cabal/users-guide/installing-packages.html>
> 
> Managing seems to imply that you should also be able to uninstall packages with a simple command.  But there seem to be no instructions for how to do this for an installed packaged.  What am I missing?  Is it called ?deregistering??
> 
> Thanks again, 
> 
> P.
> 
> _______________________________________________
> cabal-devel mailing list
> cabal-devel at haskell.org <mailto:cabal-devel at haskell.org>
> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel <http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel>
> 
> 

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From adam at bergmark.nl  Sat Aug  1 15:03:24 2015
From: adam at bergmark.nl (Adam Bergmark)
Date: Sat, 1 Aug 2015 17:03:24 +0200
Subject: Newbie: Can't understand cabal errors during install of hakyll
In-Reply-To: <CACnqJZaHNhU5Y9r=v59ya4x2V-NVxoriWxMvj+_qs6G+XrO2UA@mail.gmail.com>
References: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC@gmail.com>
 <CACnqJZaHNhU5Y9r=v59ya4x2V-NVxoriWxMvj+_qs6G+XrO2UA@mail.gmail.com>
Message-ID: <CACnqJZa5P++8zR_HmbT_knK8xSfM4S9wfX+KBf-wkusSmj+q5A@mail.gmail.com>

I sent a pull request to add time 1.4.* support to hakyll:
https://github.com/jaspervdj/hakyll/pull/360

Might make it easier for <7.10 users in the future.

- Adam


On Sat, Aug 1, 2015 at 3:34 PM, Adam Bergmark <adam at bergmark.nl> wrote:

> It seems like you have time-1.4.2 installed, the latest GHC (7.10) comes
> with time 1.5.*. Are you sure you are on 7.10?
>
> The core of the problem is that hakyll needs time >= 1.5, and unix is
> using the pre-installed time-1.4.2. This is rejected because only one
> version of a library can be used in the same install plan.
>
> As the error message suggests you can you increase the backjump limit so
> I'd try that first. I typically pass --reorder-goals --max-backjumps=-1 to
> cabal-install. Running this sometimes takes a long time, but it will finish
> eventually.
>
> You can also try installing an older version of hakyll that works with
> time-1.4.2 (see the hackage page for info on older versions).
>
> Lastly,  are you using a sandbox? It also helps with reducing problems. I
> never install anything in the global or user level package db, only in
> sandboxes.
>
> HTH,
> Adam
>
>
>
> On Sat, Aug 1, 2015 at 2:36 PM, Peder Jakobsen <pjakobsen at gmail.com>
> wrote:
>
>> Hi,
>>
>> Been with Haskell just for few days, and thought it would be a good
>> exercise to run a static site generator to get familiar with various tools,
>> and I?m already running into ?cabal hell? I think.  :(
>>
>>
>> $ cabal install hakyll
>> Resolving dependencies...
>> cabal: Could not resolve dependencies:
>> trying: hakyll-4.7.2.0 (user goal)
>> next goal: time (dependency of hakyll-4.7.2.0)
>> rejecting: time-1.4.2/installed-d67... (conflict: hakyll => time>=1.5 &&
>> <1.6)
>> trying: time-1.5.0.1
>> trying: process-1.2.0.0/installed-3a4... (dependency of hakyll-4.7.2.0)
>> next goal: unix (dependency of process-1.2.0.0/installed-3a4...)
>> rejecting: unix-2.7.0.1/installed-8ad... (conflict: time==1.5.0.1, unix =>
>> time==1.4.2/installed-d67...)
>> rejecting: unix-2.7.1.0, 2.7.0.1, 2.7.0.0, 2.6.0.1, 2.6.0.0, 2.5.1.1,
>> 2.5.1.0,
>> 2.5.0.0, 2.4.2.0, 2.4.1.0, 2.4.0.2, 2.4.0.1, 2.4.0.0, 2.3.2.0, 2.3.1.0,
>> 2.3.0.0, 2.2.0.0, 2.0 (conflict: process => unix==2.7.0.1/installed-8ad..
>> .)
>> Backjump limit reached (change with --max-backjumps).
>>
>>
>> I?m running OS X Yosemite 10.2.2 with all the latest versions of  Haskell
>> and cabal.
>>
>> Thanks  you for listening. :)
>>
>> Peder
>>
>> _______________________________________________
>> cabal-devel mailing list
>> cabal-devel at haskell.org
>> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>>
>>
>
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From cydparser at gmail.com  Sat Aug  1 20:06:04 2015
From: cydparser at gmail.com (Cyd Parser)
Date: Sat, 1 Aug 2015 13:06:04 -0700
Subject: Newbie: Can't understand cabal errors during install of hakyll
Message-ID: <CAPARmjoQBw5hO3fAs770S9-YSsMMYnQw1wA7BpX+oZVy2qqb2w@mail.gmail.com>

Hi Peder,

I'd recommend giving stack a try (https://github.com/commercialhaskell/stack).
I have found it easier to use than cabal-install. Many executables will
install just fine using `stack install <package-name>`. Packages that stack
has trouble creating a build plan for (like hakyll) can usually be
installed using the following:

stack unpack hakyll
cd hakyll-*
stack init
stack setup
stack install

`stack install` copies the resulting binaries to ~/.local/bin by default:
add that to your path.

Cheers,

cydparser



> Date: Sat, 1 Aug 2015 08:36:55 -0400
> From: Peder Jakobsen <pjakobsen at gmail.com>
> To: cabal-devel at haskell.org
> Subject: Newbie: Can't understand cabal errors during install of
>         hakyll
> Message-ID: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC at gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> Been with Haskell just for few days, and thought it would be a good
> exercise to run a static site generator to get familiar with various tools,
> and I?m already running into ?cabal hell? I think.  :(
>
>
> $ cabal install hakyll
> Resolving dependencies...
> cabal: Could not resolve dependencies:
> trying: hakyll-4.7.2.0 (user goal)
> next goal: time (dependency of hakyll-4.7.2.0)
> rejecting: time-1.4.2/installed-d67... (conflict: hakyll => time>=1.5 &&
> <1.6)
> trying: time-1.5.0.1
> trying: process-1.2.0.0/installed-3a4... (dependency of hakyll-4.7.2.0)
> next goal: unix (dependency of process-1.2.0.0/installed-3a4...)
> rejecting: unix-2.7.0.1/installed-8ad... (conflict: time==1.5.0.1, unix =>
> time==1.4.2/installed-d67...)
> rejecting: unix-2.7.1.0, 2.7.0.1, 2.7.0.0, 2.6.0.1, 2.6.0.0, 2.5.1.1,
> 2.5.1.0,
> 2.5.0.0, 2.4.2.0, 2.4.1.0, 2.4.0.2, 2.4.0.1, 2.4.0.0, 2.3.2.0, 2.3.1.0,
> 2.3.0.0, 2.2.0.0, 2.0 (conflict: process => unix==2.7.0.1/installed-8ad..
> .)
> Backjump limit reached (change with --max-backjumps).
>
>
> I?m running OS X Yosemite 10.2.2 with all the latest versions of  Haskell
> and cabal.
>
> Thanks  you for listening. :)
>
> Peder
>
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From pjakobsen at gmail.com  Sun Aug  2 02:01:03 2015
From: pjakobsen at gmail.com (Peder Jakobsen)
Date: Sat, 1 Aug 2015 22:01:03 -0400
Subject: Newbie: Can't understand cabal errors during install of hakyll
In-Reply-To: <CACnqJZaHNhU5Y9r=v59ya4x2V-NVxoriWxMvj+_qs6G+XrO2UA@mail.gmail.com>
References: <D991FCF6-9271-49D9-AEB9-543F8A2F25CC@gmail.com>
 <CACnqJZaHNhU5Y9r=v59ya4x2V-NVxoriWxMvj+_qs6G+XrO2UA@mail.gmail.com>
Message-ID: <0A60E6E0-9E18-4602-8C85-FE1B97438A99@gmail.com>

Hi Adam, 

I upgraded to ghc version 7.10.2 ? that seems to have fixed the problem.

> On Aug 1, 2015, at 9:34 AM, Adam Bergmark <adam at bergmark.nl> wrote:
> 
> Lastly,  are you using a sandbox? It also helps with reducing problems. I never install anything in the global or user level package db, only in sandboxes

Yes, I?m using a sandbox, although made the mistake of not using --only-dependencies when I did $ cabal install hakyll, and it?s been 20+ minutes, and my CPU is still grinding away.  ;)

It?s nothing like Python pip so far, but I?m sure there are good reasons why (e.g., need to compile every dependency)

Thanks again

P. 

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From pjakobsen at gmail.com  Sun Aug  2 02:19:42 2015
From: pjakobsen at gmail.com (Peder Jakobsen)
Date: Sat, 1 Aug 2015 22:19:42 -0400
Subject: --only-depencies saves time?
Message-ID: <8C1D1C08-20C2-4338-B15D-B57EE34E26F2@gmail.com>

I?ve read the Simple Guide to Cabal at http://katychuang.com/cabal-guide/ <http://katychuang.com/cabal-guide/>

It says:

create a copy of a package by running the command
cabal install
Some flags can speed up this process
--only-dependencies
-jN to build N packages in parallel
--dry-run to see what cabal plans to do (recommended)

But here?s the thing (piping a word count from ?dry-run) 

$ cabal install hakyll --dry-run | wc -l     
	 97
cabal install hakyll --only-dependencies  --dry-run | wc -l
      96

So it takes 20+ minutes to install a package that you just want to check out for a few minutes, while your CPU melts down in the process?  I must be missing something here??

Thanks again for your newbie support, greatly appreciated. 

P.J. 



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From cma at bitemyapp.com  Sun Aug  2 02:27:18 2015
From: cma at bitemyapp.com (Christopher Allen)
Date: Sat, 1 Aug 2015 21:27:18 -0500
Subject: --only-depencies saves time?
In-Reply-To: <8C1D1C08-20C2-4338-B15D-B57EE34E26F2@gmail.com>
References: <8C1D1C08-20C2-4338-B15D-B57EE34E26F2@gmail.com>
Message-ID: <CADnndOr4ZxqXyrM1HCZ5uBpnyaucW8nbJSBfxnAO-uhRapiRoQ@mail.gmail.com>

Best way to avoid this problem in my experience is to use something that'll
cache dependencies so that you're building as few new packages as possible
when checking something out. Historically people have used their user
package-dbs or sandboxes (just package-dbs you put in a place), but there's
nothing done to ensure versions won't start conflicting as the arrow of
time plunges forward.

To that end, I think Stack[1] is pretty useful as you can pick a default
(global to you) user snapshot and everything the snapshot covers will have
a set of versions that work with everything else. This doesn't cover
absolutely everything on Hackage but it should save a lot of build time if
you're going on a library perambulation.

There's no reason, in principle, that you couldn't accomplish the same with
careful tending of a package-db yourself, but in practice nobody knows or
cares to know how anything works so its best to just give them something
they can outsource their executive functions to WRT package versioning.

[1]: https://github.com/commercialhaskell/stack

On Sat, Aug 1, 2015 at 9:19 PM, Peder Jakobsen <pjakobsen at gmail.com> wrote:

> I?ve read the Simple Guide to Cabal at http://katychuang.com/cabal-guide/
>
> It says:
>
> create a copy of a package by running the command
> cabal install
> Some flags can speed up this process
> --only-dependencies
> -jN to build N packages in parallel
> --dry-run to see what cabal plans to do (recommended)
>
> But here?s the thing (piping a word count from ?dry-run)
>
> $ cabal install hakyll --dry-run | wc -l
>  97
> cabal install hakyll --only-dependencies  --dry-run | wc -l
>       96
>
> So it takes 20+ minutes to install a package that you just want to check
> out for a few minutes, while your CPU melts down in the process?  I must be
> missing something here??
>
> Thanks again for your newbie support, greatly appreciated.
>
> P.J.
>
>
>
>
> _______________________________________________
> cabal-devel mailing list
> cabal-devel at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel
>
>


-- 
Chris Allen
Currently working on http://haskellbook.com
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From gdweber at iue.edu  Tue Aug  4 16:39:22 2015
From: gdweber at iue.edu (gdweber at iue.edu)
Date: Tue, 4 Aug 2015 12:39:22 -0400
Subject: --only-depencies saves time?
In-Reply-To: <8C1D1C08-20C2-4338-B15D-B57EE34E26F2@gmail.com>
References: <8C1D1C08-20C2-4338-B15D-B57EE34E26F2@gmail.com>
Message-ID: <20150804163922.GB785@sparrow.localnet>

Hello, Peder,

On 2015-Aug-01, Peder Jakobsen wrote:
> I?ve read the Simple Guide to Cabal at http://katychuang.com/cabal-guide/ <http://katychuang.com/cabal-guide/>

The page you are referring to does not explain the flags that
it recommends.

> 
> It says:
> 
> create a copy of a package by running the command
> cabal install
> Some flags can speed up this process
> --only-dependencies

Would install all the dependencies of hakyll, but not hakyll itself.
Not much of a time saver, in this case, since there are 96 packages
on which hackyll depends.  I don't really see much point in this option.

> -jN to build N packages in parallel

I have four cores, so I routinely use -j4.
It could speed up the build by not more than 400% in that case.
Generally, for a build like this, it makes good use (> 90%) of all my CPUs,
until towards the end when there are < 4 packages remaining.

> --dry-run to see what cabal plans to do (recommended)

This one might save time, because it doesn't install anything;
it just prints out what cabal would install.  Could be useful in case
you want to scan through the list, and if you see anything
that you don't want, or it's just too long, decide not to
install hakyll, for example.  (Could actually waste more of
your time, in case you decide to build the package anyway.)

I think maybe this is more useful when _not_ using a sandbox,
because you could see if the packages it would install would
conflict with some that you already have installed?

> 
> But here?s the thing (piping a word count from ?dry-run) 
> 
> $ cabal install hakyll --dry-run | wc -l     
> 	 97
> cabal install hakyll --only-dependencies  --dry-run | wc -l
>       96
> 
> So it takes 20+ minutes to install a package that you just want to check out for a few minutes, while your CPU melts down in the process?  I must be missing something here??
>

The hakyll package is interesting and complex, and I don't see much point
in checking it out for just "a few minutes" :-)

In my case, `time cabal install -j4 hakyll` (in a sandbox) reports that
it took 13 minutes and 38 seconds.

But this is not too uncommon for installing software from source,
whether it's Haskell + cabal or C + `make configure; make; make install` ,
is it, even if we have binaries for most of the C libraries already installed?

> Thanks again for your newbie support, greatly appreciated. 
> 
> P.J.

Thanks for asking a question that was easy enough for me to answer --
it's something that doesn't happen often on this list ;-)

> 
> 
> 

> _______________________________________________
> cabal-devel mailing list
> cabal-devel at haskell.org
> http://mail.haskell.org/cgi-bin/mailman/listinfo/cabal-devel


-- 
Gregory D. Weber, Ph. D.                  http://pages.iu.edu/~gdweber/
Associate Professor of Informatics        Tel (765) 973-8420
Indiana University East                   FAX (765) 973-8550


From michael at snoyman.com  Mon Aug 17 08:59:17 2015
From: michael at snoyman.com (Michael Snoyman)
Date: Mon, 17 Aug 2015 11:59:17 +0300
Subject: Pull request 2617 (don't require global package database)
Message-ID: <CAKA2Jg+1jejrDbVQooy8ScDBLMP4GPXUCwgYQ66iAdm7e+J5_w@mail.gmail.com>

A few months ago I noticed that pull request 2617[1] implements a change
I'd love to see in Cabal: not requiring a global package database for GHCs
that support this (7.6 and on). The change is small and self-contained, and
looks like a good one to me, but it hasn't been merged. Any chance someone
with a commit bit could review?

[1] https://github.com/haskell/cabal/pull/2617
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From hvr at gnu.org  Sat Aug 29 06:56:53 2015
From: hvr at gnu.org (Herbert Valerio Riedel)
Date: Sat, 29 Aug 2015 08:56:53 +0200
Subject: Please help beta test "no-reinstall Cabal" (was: Cabal and
 simultaneous installations of the same package)
In-Reply-To: <68326f3ebbd943768effe6b0f2ff522c@DB4PR30MB030.064d.mgd.msft.net>
 (Simon Peyton Jones's message of "Mon, 23 Mar 2015 08:45:48 +0000")
References: <68326f3ebbd943768effe6b0f2ff522c@DB4PR30MB030.064d.mgd.msft.net>
Message-ID: <87fv32lgzu.fsf@gmail.com>

Good news, everyone!

...you may be interested to know this has finally come to fruition (just
in time for HIW):

  http://blog.ezyang.com/2015/08/help-us-beta-test-no-reinstall-cabal/

Cheers,
  hvr

On 2015-03-23 at 09:45:48 +0100, Simon Peyton Jones wrote:
> Dear Cabal developers
>
> You'll probably have seen the thread about the Haskell Platform.
>
> Among other things, this point arose:
>
> |  Another thing we should fix is the (now false) impression that HP gets in
> |  the way of installing other packages and versions due to cabal hell.
>
> People mean different things by "cabal hell", but the inability to 
> 	simultaneously install multiple versions of the same package,
> 	compiled against different dependencies
> is certainly one of them, and I think it is the one that Yitzchak is referring to here.
>
> But some time now GHC has allowed multiple versions of the same
> package (compiled against different dependencies) to be installed
> simultaneously.  So all we need to do is to fix Cabal to allow it too,
> and thereby kill of a huge class of cabal-hell problems at one blow.
>
> But time has passed and it hasn't happened. Is this because I'm misunderstanding?  Or because it is harder than I think?  Or because there are much bigger problems?  Or because there is insufficient effort available?  Or what?
>
> Unless I'm way off beam, this "multiple installations of the same package" thing has been a huge pain forever, and the solution is within our grasp.  What's stopping us grasping it?