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Today's Topics:
1. Re: cabal install errors & issues (Gregory Guthrie)
2. Backtrace when a certain location in the code is executed
(Nathan H?sken)
3. Re: cabal install errors & issues (Benjamin Edwards)
4. Re: Backtrace when a certain location in the code is
executed (Bryce Verdier)
5. Re: cabal install errors & issues (Gregory Guthrie)
6. Re: cabal install errors & issues (Benjamin Edwards)
7. Re: source code for "Generics for the Masses" (Stephen Tetley)
----------------------------------------------------------------------
Message: 1
Date: Thu, 16 Aug 2012 08:18:31 -0500
From: Gregory Guthrie <[email protected]>
Subject: Re: [Haskell-beginners] cabal install errors & issues
To: "[email protected]" <[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="us-ascii"
Thanks for the advice and pointers, I will try to make this transition, but it
looks like it is not so simple.
Trying to bootstrap into cabal-dev seems to require some external installations
as well;
>>cabal install cabal-dev --force-reinstalls
...
Configuring network-2.3.0.14...
cabal: The package has a './configure' script. This requires a Unix
compatibility toolchain such as MinGW+MSYS or Cygwin.
cabal: Error: some packages failed to install:
HTTP-4000.2.3 depends on network-2.3.0.14 which failed to install.
cabal-dev-0.9.1 depends on network-2.3.0.14 which failed to install.
network-2.3.0.14 failed during the configure step. The exception was:
ExitFailure 1
I do have MinGW+MSYS installed, might be a PATH issue, I'll check further.
I don't understand the details of Haskell package management, and the
implications of this description of cabal-dev:
For installed packages, the sandboxing means that packages are not
registered into the user or global ghc package database.
The global package db is used, so it is recommended that the global
package db is only used for the ghc core libraries.
This approach conflicts with using distribution packages for non-core
libraries, because they are installed into the global db.
It seems odd to me to say that "they are not registered.." into either
database, and then say the global package db is used. Is there some distinction
here between a "global ghc package db" & a "global package db"?.
Cabal install hsenv shows "no such package", and I'm not sure why using it with
installs would be good.
Already removing shadowing packages is breaking things, so more cleanup will
also be needed for that.
I am trying to convert some SML classes and labs for my students to Haskell,
and all of this overhead is certainly something that I couldn't wish on them!
Perhaps if I have them all start with cabal-dev none of this would happen?
-------------------------------------------
> > Please see this:
> >> http://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-
> >> is-not-a-package-manager/
> >
> > thanks Benjamin, for the cabal-dev, hsenv tip though.
------------------------------
Message: 2
Date: Thu, 16 Aug 2012 16:31:47 +0200
From: Nathan H?sken <[email protected]>
Subject: [Haskell-beginners] Backtrace when a certain location in the
code is executed
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1
Hey,
I am trying to understand haskell program not written by me.
During runtime one function is called with parameters which makes the
function throw an error. I want to know from where the function is called.
In c++ I would set a breakpoint on the error throwing code, and let gdb
print the backtrace.
To I have similar options in haskell?
What other options do I have?
Thanks!
Nathan
------------------------------
Message: 3
Date: Thu, 16 Aug 2012 15:47:32 +0100
From: Benjamin Edwards <[email protected]>
Subject: Re: [Haskell-beginners] cabal install errors & issues
To: Gregory Guthrie <[email protected]>
Cc: "[email protected]" <[email protected]>
Message-ID:
<can6k4nhsbzwjmy8cbkuf9cvwi20gx+tf6pca0ziqwy0xaoo...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Ahh, I think network is a pain to build on Windows. I don't as a rule do
any haskell on windows because of the headaches of msys / mingw.
As to cabal-dev:
I don't think I even know what the paragraph means either. The short of it
is this:
You have packages that are globally registered with ghc, and packages that
are registered on a per user basis. When you call cabal-dev install foo it
makes a build dir called cabal-dev (you can change that) and builds foo in
there and installs + registers and deps that weren't in the global or user
database in there.
*phew*
hsenv: I forget that this is called virthualenv on hackage. It also allows
for sandboxing. Cabal-dev is probably easiest to start with.
You might want to read this:
http://www.reddit.com/r/haskell/comments/f3ykj/psa_use_cabaldev_to_solve_dependency_problems/
On Aug 16, 2012 2:21 PM, "Gregory Guthrie" <[email protected]> wrote:
> Thanks for the advice and pointers, I will try to make this transition,
> but it looks like it is not so simple.
>
> Trying to bootstrap into cabal-dev seems to require some external
> installations as well;
>
> >>cabal install cabal-dev --force-reinstalls
> ...
> Configuring network-2.3.0.14...
> cabal: The package has a './configure' script. This requires a Unix
> compatibility toolchain such as MinGW+MSYS or Cygwin.
> cabal: Error: some packages failed to install:
> HTTP-4000.2.3 depends on network-2.3.0.14 which failed to install.
> cabal-dev-0.9.1 depends on network-2.3.0.14 which failed to install.
> network-2.3.0.14 failed during the configure step. The exception was:
> ExitFailure 1
>
> I do have MinGW+MSYS installed, might be a PATH issue, I'll check further.
>
> I don't understand the details of Haskell package management, and the
> implications of this description of cabal-dev:
>
> For installed packages, the sandboxing means that packages are not
> registered into the user or global ghc package database.
> The global package db is used, so it is recommended that the global
> package db is only used for the ghc core libraries.
> This approach conflicts with using distribution packages for
> non-core libraries, because they are installed into the global db.
>
> It seems odd to me to say that "they are not registered.." into either
> database, and then say the global package db is used. Is there some
> distinction here between a "global ghc package db" & a "global package db"?.
>
> Cabal install hsenv shows "no such package", and I'm not sure why using it
> with installs would be good.
>
> Already removing shadowing packages is breaking things, so more cleanup
> will also be needed for that.
>
> I am trying to convert some SML classes and labs for my students to
> Haskell, and all of this overhead is certainly something that I couldn't
> wish on them! Perhaps if I have them all start with cabal-dev none of this
> would happen?
>
> -------------------------------------------
> > > Please see this:
> > >> http://ivanmiljenovic.wordpress.com/2010/03/15/repeat-after-me-cabal-
> > >> is-not-a-package-manager/
> > >
> > > thanks Benjamin, for the cabal-dev, hsenv tip though.
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
>
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Message: 4
Date: Thu, 16 Aug 2012 10:05:50 -0700
From: Bryce Verdier <[email protected]>
Subject: Re: [Haskell-beginners] Backtrace when a certain location in
the code is executed
To: [email protected]
Message-ID: <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I'm aware of :break in ghci, and I've used it for "little" functions
that I was trying to understand. I'm not sure how well it'll work for a
large project though.
This is the "debugging" section in ghci when you type ":help":
-- Commands for debugging:
:abandon at a breakpoint, abandon current computation
:back go back in the history (after :trace)
:break [<mod>] <l> [<col>] set a breakpoint at the specified location
:break <name> set a breakpoint on the specified function
:continue resume after a breakpoint
:delete <number> delete the specified breakpoint
:delete * delete all breakpoints
:force <expr> print <expr>, forcing unevaluated parts
:forward go forward in the history (after :back)
:history [<n>] after :trace, show the execution history
:list show the source code around current
breakpoint
:list identifier show the source code for <identifier>
:list [<module>] <line> show the source code around line number
<line>
:print [<name> ...] prints a value without forcing its
computation
:sprint [<name> ...] simplifed version of :print
:step single-step after stopping at a breakpoint
:step <expr> single-step into <expr>
:steplocal single-step within the current top-level
binding
:stepmodule single-step restricted to the current module
:trace trace after stopping at a breakpoint
:trace <expr> evaluate <expr> with tracing on (see
:history)
I hope this helps.
Bryce
On 8/16/12 7:31 AM, Nathan H?sken wrote:
> Hey,
>
> I am trying to understand haskell program not written by me.
> During runtime one function is called with parameters which makes the
> function throw an error. I want to know from where the function is called.
>
> In c++ I would set a breakpoint on the error throwing code, and let gdb
> print the backtrace.
> To I have similar options in haskell?
> What other options do I have?
>
> Thanks!
> Nathan
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
------------------------------
Message: 5
Date: Thu, 16 Aug 2012 12:25:50 -0500
From: Gregory Guthrie <[email protected]>
Subject: Re: [Haskell-beginners] cabal install errors & issues
To: Benjamin Edwards <[email protected]>
Cc: "[email protected]" <[email protected]>
Message-ID:
<[email protected]>
Content-Type: text/plain; charset="us-ascii"
Thanks for the clarification and info.
>From this I then deduce:
Using "cabal install" is dangerous, and leads to broken package structure
(inconsistent package versions and shadowing).
Better to use cabal-dev,
But it requires network, which is external to Haskell, and a pain to build
(on windows)...
Thus, no good solution on Windows - is this right?
Since Windows is 94%+ of computing environments today (all of our labs use
Windows, and "standard" IDEs), then Haskell is not a good fit?
We want to use Windows since that is what students will generally see in their
professional environments.
I hope not...!! :-)
-------------------------------------------------------
>> Ahh, I think network is a pain to build on Windows.
>> I don't as a rule do any haskell on windows because of the headaches of
>> msys / mingw.
------------------------------
Message: 6
Date: Thu, 16 Aug 2012 18:50:26 +0100
From: Benjamin Edwards <[email protected]>
Subject: Re: [Haskell-beginners] cabal install errors & issues
To: Gregory Guthrie <[email protected]>
Cc: "[email protected]" <[email protected]>
Message-ID:
<CAN6k4ngOPxeyqLngfJ9=1xgujbBcLR23xxHN4wGc2CQ=2f9...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
It really depends on what you are looking to teach!
For professional dev with lots of packages and different projects then
sandboxing is a must.
I imagine for a lab you could get away with what's in the haskell platform.
I got cabal-dev going on a windows box not too long ago. When I get home I
will have a tinker.
I am sure someone with more windows experience than I can chime in.
On Aug 16, 2012 6:28 PM, "Gregory Guthrie" <[email protected]> wrote:
> Thanks for the clarification and info.
>
> From this I then deduce:
> Using "cabal install" is dangerous, and leads to broken package
> structure (inconsistent package versions and shadowing).
> Better to use cabal-dev,
> But it requires network, which is external to Haskell, and a pain to
> build (on windows)...
>
> Thus, no good solution on Windows - is this right?
>
> Since Windows is 94%+ of computing environments today (all of our labs use
> Windows, and "standard" IDEs), then Haskell is not a good fit?
> We want to use Windows since that is what students will generally see in
> their professional environments.
>
> I hope not...!! :-)
>
> -------------------------------------------------------
>
> >> Ahh, I think network is a pain to build on Windows.
> >> I don't as a rule do any haskell on windows because of the headaches
> of msys / mingw.
>
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Message: 7
Date: Thu, 16 Aug 2012 19:12:12 +0100
From: Stephen Tetley <[email protected]>
Subject: Re: [Haskell-beginners] source code for "Generics for the
Masses"
To: Michael Litchard <[email protected]>
Cc: [email protected]
Message-ID:
<cab2tprbbblsestthohdje_dmhabxxnb0z-wmpqxkv0zh4hx...@mail.gmail.com>
Content-Type: text/plain; charset="iso-8859-1"
Hello Michael
Here's a copy - at 8KB it doesn't seem _too_ heinous to post it to the list.
On 16 August 2012 01:03, Michael Litchard <[email protected]> wrote:
> In the paper by Ralf Hinze, "Generics for the Masses", there is
> reference to code one may play with. But the link,
> http://www.ralf-hinze.de/masses.tar.bz2 is dead. I know someone,
> somewhere has this file. Could you point me to where it lives?
>
> _______________________________________________
> Beginners mailing list
> [email protected]
> http://www.haskell.org/mailman/listinfo/beginners
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