Is there a way to load a package(s) using Stack in GHCI and play around with it ?
So, that when the ghci is loaded, we can import the modules and see it's type signature, etc.
For the packages present in Stackage,
$ stack ghci --package unix-time
And this will give you a repl with the package unix-time loaded in it:
Run from outside a project, using implicit global project config
Using resolver: lts-6.14 from implicit global project's config file: /home/sibi/.stack/global-project/stack.yaml
GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
λ> import Data.UnixTime
λ> :t getUnixTime
getUnixTime :: IO UnixTime
For multiple packages:
$ stack ghci --package unix-time --package download
Run from outside a project, using implicit global project config
Using resolver: lts-6.14 from implicit global project's config file: /home/sibi/.stack/global-project/stack.yaml
tagsoup-0.13.10: using precompiled package
xml-1.3.14: using precompiled package
time-locale-compat-0.1.1.3: using precompiled package
feed-0.3.11.1: download
feed-0.3.11.1: configure
feed-0.3.11.1: build
feed-0.3.11.1: copy/register
download-0.3.2.4: download
download-0.3.2.4: configure
download-0.3.2.4: build
download-0.3.2.4: copy/register
Completed 5 action(s).
Configuring GHCi with the following packages:
GHCi, version 7.10.3: http://www.haskell.org/ghc/ :? for help
Ok, modules loaded: none.
λ> import Network.Download
λ>
Related
I am currently self studying Haskell. I am just a beginner so I haven't yet had a need to use cabal or stack. But right now I need to test some of my code using QuickCheck.
From this link that I found https://github.com/haskell/cabal/blob/master/doc/cabal-commands.rst , I ran the command cabal install --lib QuickCheck --package-env . and got the following output :
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install --lib QuickCheck --package-env .
Resolving dependencies...
Up to date
In the same directory, I have a .hs file and in that when I tried to import Test.QuickCheck the linter gives an error as the package doesnt seem to be available for importing.
Then I ran cabal repl --build-depends QuickCheck and then in ghci I was able to import it. But still it was not importing in the code file.
Then when I just opened ghci by firing the command ghci , the following shows up, which suggests that there is a package environment here in this directory :
GHCi, version 8.10.7: [https://www.haskell.org/ghc/](https://www.haskell.org/ghc/) :? for help
Loaded package environment from /home/axiom/Desktop/Haskell-Learning/Course/Homework 10/.ghc.environment.x86\_64-linux-8.10.7
Prelude> import Test.QuickCheck
Prelude Test.QuickCheck> :q
Even after above, that is, being able to import QuickCheck in GHCi, the import is still not working in the file.
After this, I tried the following :
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install QuickCheck
Resolving dependencies...
Up to date
Warning:
############################################################
# WARNING: Installation might not be completed as desired! #
############################################################
The command "cabal install [TARGETS]" doesn't expose libraries.
* You might have wanted to add them as dependencies to your package. In this
case add "QuickCheck" to the build-depends field(s) of your package's .cabal
file.
* You might have wanted to add them to a GHC environment. In this case use
"cabal install --lib QuickCheck". The "--lib" flag is provisional: see
https://github.com/haskell/cabal/issues/6481 for more information.
axiom#pop-os:~/Desktop/Haskell-Learning/Course/Homework 10$ cabal install --lib QuickCheck
Resolving dependencies...
Up to date
The import still doesn't work.
Any help is appreciated !
The method I ended up finding is the following :
Run the following in the directory where you have your haskell file where you want to import an external package :
cabal init
This will general a small number of files and such in that directory.
Add the name of the package that you want to use in the .cabal file that was generated . For example, I wanted to use QuickCheck so my .cabal file looks like this :
cabal-version: 2.4
name: Homework10
version: 0.1.0.0
author: Name Surname
maintainer: name#email.com
extra-source-files: CHANGELOG.md
executable Homework10
main-is: Main.hs
build-depends: base ^>=4.14.3.0, QuickCheck
hs-source-dirs: app
default-language: Haskell2010
Then in the same directory, run the following :
cabal build
Then when you try to import the package in your .hs, you should be able to do so.
I'm using stack ghci to start my REPL, based on the answer I got for my question on how to import a module installed with stack. This works fine, but I get initially a warning message Note: No local targets specified, so a plain ghci will be started with no package hiding or package options., followed by a bunch of suggestions about package hiding and options. My guess is that this is because I have not used stack init to setup a project, since I am still in the "playing around and learning" state and don't want a project yet. I have not found an explanation about the meaning of 'no local targets', but the effect to start a plain ghci is exactly what I want at that point. Is there a way to suppress this message? I looked at stack --help, but could not find something suitable.
As the Note (not warning) suggests, a plain ghci is started, which is rather uncommon situation when working with stack.
~$ stack ghci
Note: No local targets specified, so a plain ghci will be started with no package hiding or package options.
You are using snapshot: lts-14.12
If you want to use package hiding and options, then you can try one of the following:
* If you want to start a different project configuration than /home/username/.stack/global-project/stack.yaml, then you can use stack init to create a new stack.yaml for the packages in the
current directory.
* If you want to use the project configuration at /home/username/.stack/global-project/stack.yaml, then you can add to its 'packages' field.
Configuring GHCi with the following packages:
GHCi, version 8.6.5: http://www.haskell.org/ghc/ :? for help
Loaded GHCi configuration from /tmp/haskell-stack-ghci/2a3bbd58/ghci-script
Prelude>
This means though that all you need to do to get the same behavior without the Note is just start ghci manually in the context of global stack environment:
~$ stack exec -- ghci
GHCi, version 8.6.5: http://www.haskell.org/ghc/ :? for help
Prelude>
In case that you want to make sure some package is installed for "playing around and learning" in the ghci session you can supply them as --package arguments
~$ stack exec --package massiv -- ghci
atomic-primops> using precompiled package
cabal-doctest > using precompiled package
scheduler > using precompiled package
massiv > using precompiled package
Completed 4 action(s).
GHCi, version 8.6.5: http://www.haskell.org/ghc/ :? for help
Prelude> import Data.Massiv.Array
Prelude Data.Massiv.Array>
stack exec --ghci as in lehins's answer did not work for me, but stack exec ghci did.
I installed diagrams, and it seems to be there, but GHCi doesn’t find it. I tried adding the local sandbox to the command line (-package-db), but still no luck.
Any suggestions?
C:\Users\guthrie>
C:\Users\guthrie>cabal install diagrams
Resolving dependencies...
All the requested packages are already installed:
diagrams-1.2
Use --reinstall if you want to reinstall anyway.
I find it in:
C:\Users\guthrie\.cabal-sandbox\i386-windows-ghc-7.6.3-packages.conf.d
(diagrams-1.2, diagrams-contrib, -core, -lib, -svg)
But running: “cabal repl” or using the GHC(i) flag “-package-db=…”
fail to find it:
C:\Users\guthrie>cabal repl
GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :m + Diagrams.Prelude
<no location info>:
Could not find module `Diagrams.Prelude'
It is not a module in the current program, or in any known package.
Prelude>
To clarify; ignoring the cabal invocations, using GHC/i directly, and the program diagramsDemo.hs:
-- http://projects.haskell.org/diagrams/doc/quickstart.html
--
import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine
main = mainWith (circle 1 :: Diagram B R2)
Gives:
C:\Users\guthrie\Desktop\xFer\Graphics>ghc --make diagramsDemo.hs
diagramsDemo.hs:7:8:
Could not find module `Diagrams.Backend.SVG.CmdLine'
Use -v to see a list of the files searched for.
C:\Users\guthrie\Desktop\xFer\Graphics>ghc --make diagramsDemo.hs -package-db=C:\Users\guthrie\.cabal-sandbox\i386-windows-ghc-7.6.3-packages.conf.d
diagramsDemo.hs:7:8:
Could not find module `Diagrams.Backend.SVG.CmdLine'
Use -v to see a list of the files searched for.
As bheklilr said, if ghci is started with cabal repl, it will only find packages specified as a dependency in the .cabal file.
However you can start it with cabal exec ghci, then it will find all packages installed in the sandbox.
The same is true for invoking ghc (cabal build vs. cabal exec ghc), but note that if you want to pass flags you have to use --, like in cabal exec ghc -- -O2 Main.hs. Alternatively you can use cabal exec bash and launch ghci or ghc in the new shell.
cabal exec was added with Cabal 1.20.
I am trying to get a project running that uses conduit and conduit-extra. This is the main module:
import Data.Conduit
main = do
putStrLn "Done"
The cabal file requires base, conduit and conduit-extra:
...
build-depends: base >=4.8 && <4.9,
conduit >=1.2.5 && <1.3,
conduit-extra >= 1.1.9.1 && <1.2
...
Yet when I run cabal repl, this happens:
Johns-iMac:The-Project john$ cabal repl
Preprocessing executable 'The-Project' for The-Project-0.1.0.0...
GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help
<command line>: can't load .so/.DLL for: /Library/Haskell/ghc-7.10.2-x86_64/lib/exceptions-0.8.0.2/libHSexceptions-0.8.0.2-8GsEeHgaIks3pVGk6GaELJ-ghc7.10.2.dylib (dlopen(/Library/Haskell/ghc-7.10.2-x86_64/lib/exceptions-0.8.0.2/libHSexceptions-0.8.0.2-8GsEeHgaIks3pVGk6GaELJ-ghc7.10.2.dylib, 5): Library not loaded: #rpath/libHStransformers-compat-0.4.0.4-DCQioW2d4vYEa3T0AmFBPv-ghc7.10.2.dylib
Referenced from: /Library/Haskell/ghc-7.10.2-x86_64/lib/exceptions-0.8.0.2/libHSexceptions-0.8.0.2-8GsEeHgaIks3pVGk6GaELJ-ghc7.10.2.dylib
Reason: image not found)
I just completely reinstalled the Haskell Platform, and it's all sandboxed, so there shouldn't be any problems with competing dependencies.
What is happening, and how do I fix it?
UPDATE:
I deleted the sandbox (cabal.sandbox.config, .cabal-sandbox), and reinstalled the dependencies:
cabal sandbox init
cabal install --only-dependencies
cabal repl
We now have a new but very similar error:
Johns-iMac:The-Project john$ cabal repl
Preprocessing executable 'The-Project' for The-Project-0.1.0.0...
GHCi, version 7.10.2: http://www.haskell.org/ghc/ :? for help
<command line>: can't load .so/.DLL for: /Library/Haskell/ghc-7.10.2-x86_64/lib/hashable-1.2.3.3/libHShashable-1.2.3.3-2GTZqecVp8NJZrNuKzGxfy-ghc7.10.2.dylib (dlopen(/Library/Haskell/ghc-7.10.2-x86_64/lib/hashable-1.2.3.3/libHShashable-1.2.3.3-2GTZqecVp8NJZrNuKzGxfy-ghc7.10.2.dylib, 5): Library not loaded: #rpath/libHStext-1.2.1.3-1l1AN4I48k37RaQ6fm6CEh-ghc7.10.2.dylib
Referenced from: /Library/Haskell/ghc-7.10.2-x86_64/lib/hashable-1.2.3.3/libHShashable-1.2.3.3-2GTZqecVp8NJZrNuKzGxfy-ghc7.10.2.dylib
Reason: image not found)
Given that this report refers to a problem loading hashable, and the Github report refers to a problem loading exceptions, both of which are packages provided by the platform and not GHC, I have a feeling there's a problem with the platform installer. Can you try again with either GHC for Mac OS X or stack and see if it resolves the issue?
Note that, if you go the stack route, you'll want to run stack init && stack build --install-ghc && stack ghci in your project. In either case: you'll probably be safer if you completely remove the platform install first.
I installed diagrams, and it seems to be there, but GHCi doesn’t find it. I tried adding the local sandbox to the command line (-package-db), but still no luck.
Any suggestions?
C:\Users\guthrie>
C:\Users\guthrie>cabal install diagrams
Resolving dependencies...
All the requested packages are already installed:
diagrams-1.2
Use --reinstall if you want to reinstall anyway.
I find it in:
C:\Users\guthrie\.cabal-sandbox\i386-windows-ghc-7.6.3-packages.conf.d
(diagrams-1.2, diagrams-contrib, -core, -lib, -svg)
But running: “cabal repl” or using the GHC(i) flag “-package-db=…”
fail to find it:
C:\Users\guthrie>cabal repl
GHCi, version 7.6.3: http://www.haskell.org/ghc/ :? for help
Loading package ghc-prim ... linking ... done.
Loading package integer-gmp ... linking ... done.
Loading package base ... linking ... done.
Prelude> :m + Diagrams.Prelude
<no location info>:
Could not find module `Diagrams.Prelude'
It is not a module in the current program, or in any known package.
Prelude>
To clarify; ignoring the cabal invocations, using GHC/i directly, and the program diagramsDemo.hs:
-- http://projects.haskell.org/diagrams/doc/quickstart.html
--
import Diagrams.Prelude
import Diagrams.Backend.SVG.CmdLine
main = mainWith (circle 1 :: Diagram B R2)
Gives:
C:\Users\guthrie\Desktop\xFer\Graphics>ghc --make diagramsDemo.hs
diagramsDemo.hs:7:8:
Could not find module `Diagrams.Backend.SVG.CmdLine'
Use -v to see a list of the files searched for.
C:\Users\guthrie\Desktop\xFer\Graphics>ghc --make diagramsDemo.hs -package-db=C:\Users\guthrie\.cabal-sandbox\i386-windows-ghc-7.6.3-packages.conf.d
diagramsDemo.hs:7:8:
Could not find module `Diagrams.Backend.SVG.CmdLine'
Use -v to see a list of the files searched for.
As bheklilr said, if ghci is started with cabal repl, it will only find packages specified as a dependency in the .cabal file.
However you can start it with cabal exec ghci, then it will find all packages installed in the sandbox.
The same is true for invoking ghc (cabal build vs. cabal exec ghc), but note that if you want to pass flags you have to use --, like in cabal exec ghc -- -O2 Main.hs. Alternatively you can use cabal exec bash and launch ghci or ghc in the new shell.
cabal exec was added with Cabal 1.20.