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Today's Topics:
1. Why is cabal trying to install a particular dependency? (Peter)
2. Re: Why is cabal trying to install a particular dependency?
(Ben Gamari)
3. Re: Why is cabal trying to install a particular dependency?
(Peter)
4. Re: Haskeline and forkIO (Peter Jones)
5. Re: Why is cabal trying to install a particular
dependency?
(Gesh)
----------------------------------------------------------------------
Message: 1
Date: Thu, 28 Aug 2014 12:18:53 +0000 (UTC)
From: Peter <[email protected]>
To: [email protected]
Subject: [Haskell-beginners] Why is cabal trying to install a
particular dependency?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
Sometimes I want to know why installing package X will require package Y.
After a lot of recursive manual inspection of .cabal files and --dry-run, I
discover that X depends on A, which depends on B, which depends on C, which
requires Y unless some flag is specified.
Is there a way to ask cabal to tell me this?
------------------------------
Message: 2
Date: Thu, 28 Aug 2014 08:38:47 -0400
From: Ben Gamari <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Why is cabal trying to install a
particular dependency?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
On August 28, 2014 8:18:53 AM EDT, Peter <[email protected]> wrote:
>Sometimes I want to know why installing package X will require package
>Y.
>After a lot of recursive manual inspection of .cabal files and
>--dry-run, I
>discover that X depends on A, which depends on B, which depends on C,
>which
>requires Y unless some flag is specified.
>
>Is there a way to ask cabal to tell me this?
>
Passing -v3 to cabal will cause it to emit all manner of useful (and less than
useful) information. It's particularly handy when trying to identify which
package is holding back a dependency.
Unfortunately it can be a bit tricky to quickly parse but grep can help here.
Cheers,
- Ben
------------------------------
Message: 3
Date: Thu, 28 Aug 2014 13:40:43 +0000 (UTC)
From: Peter <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] Why is cabal trying to install a
particular dependency?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=us-ascii
Ben Gamari <ben <at> smart-cactus.org> writes:
> Passing -v3 to cabal will cause it to emit all manner of useful (and less
than useful) information. It's
> particularly handy when trying to identify which package is holding back a
dependency.
>
> Unfortunately it can be a bit tricky to quickly parse but grep can help here.
Not ideal, but a definite improvement on what I was doing before!
------------------------------
Message: 4
Date: Thu, 28 Aug 2014 08:11:15 -0600
From: Peter Jones <[email protected]>
To: [email protected]
Subject: Re: [Haskell-beginners] Haskeline and forkIO
Message-ID: <[email protected]>
Content-Type: text/plain
"Jeff C. Britton" <[email protected]> writes:
> loop :: InputT IO ()
> loop = do
> maybeLine <- getInputLine "Enter a file to compress> "
> case maybeLine of
> Nothing -> return () -- user entered EOF
> Just "" -> return () -- treat no name as "want to quit"
> Just path -> do
> return (runWorker path)
> loop
The other issue you're having is because `runWorker path` is an `IO ()`
value but at the point where you use it in the code the type system
wants an `InputT IO ()`. To try to satisfy the type system you used
`return` to build a `InputT IO (IO ())` value, but that doesn't actually
work (as you've noticed). Since `InputT` is a transformer you have an
extra layer to work through and so need to *lift* your `IO ()` value
into the `InputT IO` layer. Try this:
-- Add this import
import Control.Monad.IO.Class
loop :: InputT IO ()
loop = do
maybeLine <- getInputLine "Enter a file to compress> "
case maybeLine of
Nothing -> return () -- user entered EOF
Just "" -> return () -- treat no name as "want to quit"
Just path -> do
liftIO (runWorker path)
loop
You can think of `liftIO` as having this signature (in this context):
liftIO :: IO () -> InputT IO ()
--
Peter Jones, Founder, Devalot.com
Defending the honor of good code
------------------------------
Message: 5
Date: Thu, 28 Aug 2014 17:57:05 +0300
From: Gesh <[email protected]>
To: The Haskell-Beginners Mailing List - Discussion of primarily
beginner-level topics related to Haskell <[email protected]>
Subject: Re: [Haskell-beginners] Why is cabal trying to install a
particular dependency?
Message-ID: <[email protected]>
Content-Type: text/plain; charset=UTF-8
Wouldn't it make sense for cabal to provide a
list-dependencies command, which can query those
dependencies recursively?
Gesh
------------------------------
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