I use cabal to install QuickCheck in a sandbox environment and it looks good
C:\Users\yashi>cabal install QuickCheck
Resolving dependencies...
Notice: installing into a sandbox located at C:\Users\yashi\.cabal-sandbox
Downloading erf-2.0.0.0...
Downloading primitive-0.6.4.0...
Downloading random-1.1...
...
Installed QuickCheck-2.12.4
But when I open a file, it shows
C:\\Users\yashi\OneDrive\Desktop\Ex1.hs:24:1: error:
Could not find module ‘Test.QuickCheck’
Use -v to see a list of the files searched for.
|
24 | import Test.QuickCheck (Property, quickCheck, (==>))
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Failed, no modules loaded.
Prelude> import Test.QuickCheck
How can I fix it?
There probably isn't enough information in here on how you set up your sandbox or started GHCi for people to provide you with an answer. I can give you an approach to this that will work with Stack, however:
$ stack ghci --package QuickCheck
> import Test.QuickCheck
Related
With the release of cabal-3, the packages from Hackage are installed in a new location that the compiler ghc and ghc-pkg know nothing about.
In other words, packages are installed but not registered for ghc. Ghci, ghc, ghc-pkg cannot work.
For example,
cabal install safe --lib
Create file t1.hs
import Safe
t1 = tailMay [1,2,3]
Let's try:
> ghci t1.hs
GHCi, version 8.10.2: https://www.haskell.org/ghc/:? for help
[1 of 1] Compiling Main (t1.hs, interpreted)
t1.hs: 1: 1: error:
Could not find module `Safe '
Use -v (or `: set -v` in ghci) to see a list of the files searched for.
|
1 | import Safe
| ^^^^^^^^^^^
Failed, no modules loaded.
This bug is described here
https://github.com/haskell/cabal/issues/6262
and here
https://gitlab.haskell.org/ghc/ghc/-/issues/17341
I use as a temporary solution setting a system variable
GHC_PACKAGE_PATH=C:\Users\me\AppData\Roaming\cabal\store\ghc-8.10.2\package.db;
(Windwos 10, haskell-dev by chocolatey)
via
On Windows, packages installed with cabal seem to be unavailable in ghc/ghci
but with updates I will have to manually change this system variable.
Are there any more elegant solutions to this problem?
P.S. Unfortunately, this solution (via GHC's environment variable GHC_PACKAGE_PATH) is incompatible with Cabal :(
https://github.com/haskell/cabal/issues/1944
One way to achieve this is to use the --env flag to make the libraries available to GHC whenever you are in the current directory:
~ $ mkdir /tmp/foo
~ $ cd /tmp/foo
/tmp/foo $ cabal install safe --lib --env .
Resolving dependencies...
Build profile: -w ghc-8.8.3 -O1
In order, the following will be built (use -v for more details):
- safe-0.3.19 (lib) (requires build)
Configuring library for safe-0.3.19..
Preprocessing library for safe-0.3.19..
Building library for safe-0.3.19..
…
> Installing library in /home/jojo/.cabal/store/ghc-8.8.3/incoming/new-4056/home/jojo/.cabal/store/ghc-8.8.3/safe-0.3.19-92fbaef88124b4508ce447f6245bc793f7a1748247ae68d10e449150df1069af/lib
t1.hs
/tmp/foo $ cat > t1.hs
import Safe
t1 = tailMay [1,2,3]
/tmp/foo $ ls -a
. .. .ghc.environment.x86_64-linux-8.8.3 t1.hs
/tmp/foo $ ghci t1.hs
GHCi, version 8.8.3: https://www.haskell.org/ghc/ :? for help
Loaded package environment from /tmp/foo/.ghc.environment.x86_64-linux-8.8.3
[1 of 1] Compiling Main ( t1.hs, interpreted )
Ok, one module loaded.
*Main>
Note that you probably shouldn’t do this in a directory where you actually have a foo.cabal file. See the documentation of cabal v2-install for details.
Working with GHC_ENVIRONMENT is better:
setx GHC_ENVIRONMENT C:\Users\me\.ghc\x86_64-mingw32-8.10.2\environments\default
it helps for ghc and ghci.
After, in C:\Users\me\AppData\Roaming\cabal\config we should add
package-db: C:\Users\me\AppData\Roaming\cabal\store\ghc-8.10.2\package.db
it helps for cabal.
Unfortunately, ghc-pkg still has problem and works with such flag:
ghc-pkg list --user-package-db="C:\Users\me\AppData\Roaming\cabal\store\ghc-8.10.2\package.db"
For Linux the steps are similar.
Am working through Real World Haskell and am trying to install regex-posix-0.95.2 from an untar[ed] package by simplying running
cabal install
I then see:
Text/Regex/Posix/Wrap.hsc:141:1: error:
Could not find module ‘Text.Regex.Base.RegexLike’
There are files missing in the ‘regex-base-0.93.2’ package,
try running 'ghc-pkg check'.
Use -v to see a list of the files searched for.
|
141 | import Text.Regex.Base.RegexLike(RegexOptions(..),RegexMaker(..),RegexContext(..),MatchArray)
Despite the fact that I can load this in ghci with
Prelude> :module Text.Regex.Base.RegexLike
Prelude Text.Regex.Base.RegexLike>
Prelude> import Text.Regex.Base.RegexLike(RegexOptions(..),RegexMaker(..),RegexContext(..),MatchArray)
Prelude Text.Regex.Base.RegexLike>
and see it in the module-system.
[warrick#warrick-pc regex-posix-0.95.2]$ ghc-pkg find-module Text.Regex.Base.RegexLike
/usr/lib/ghc-8.6.2/package.conf.d
regex-base-0.93.2
Why is this failing?
What are some more general tips and tricks when trying to debug cabal failures you'd recommend (as this is one instance of many issues I'm consistently having with Cabal)?
This is a linking issue. For example, some distributions like Arch use dynamic linking by default, without static libraries, but without additional configuration, cabal tries to link statically, which results in the kind of message you are seeing. For more information: https://wiki.archlinux.org/index.php/Haskell
I tried using the primes module in Haskell and after running
$ cabal install primes
Resolving dependencies...
Notice: installing into a sandbox located at /home/christoph/.cabal-sandbox
Downloading primes-0.2.1.0...
Configuring primes-0.2.1.0...
Building primes-0.2.1.0...
Installed primes-0.2.1.0
I tried making a file with
import Data.Numbers.Primes
at the top, but every attempt to load it failed with the error message:
Could not find module ‘Data.Numbers.Primes’
Use -v to see a list of the files searched for.
The question: what am I missing here? there must be something wrong with this way of using it right?
After reading Haskell: where is Data.Numbers.Primes library? I also tried:
import Data.Primes
import primes
import Primes
but none of them worked.
Thank you in advance, any help is most welcome
Because you are installing the primes package to a sandbox, you will need to run the compiler with awareness of the sandbox. cabal offers the exec command for this, so e.g.
echo import Data.Numbers.Primes >foo.hs
cabal exec ghci foo.hs
from within the sandbox should work.
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 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.