I am very new to Haskell and I am trying to add the graphics package gloss to my stack project but I am encountering problems when doing stack build.
I have created my stack project as follows:
LICENSE package.yaml stack.yaml
README.md package.yaml~ stack.yaml.lock
Setup.hs project39.cabal stack.yaml~
TAGS project39.cabal~ test
and edited the stack.yamland the cabal file as follows:
# extra-deps:
# - acme-missiles-0.3
# - git: https://github.com/commercialhaskell/stack.git
# commit: e7b331f14bcffb8367cd58fbfc8b40ec7642100a
# - gloss-1.13.2.1
executable project39-exe
main-is: Main.hs
other-modules:
Paths_project39
hs-source-dirs:
app
ghc-options: -threaded -rtsopts -with-rtsopts=-N
build-depends:
base >=4.7 && <5
, project39
, gloss
default-language: Haskell2010
In the src file Lib.hs I have added a Import Graphics.Gloss to test if it works:
module Lib
( someFunc
) where
import Graphics.Gloss
but when I then do stack build I get the following error:
Could not load module ‘Graphics.Gloss’
It is a member of the hidden package ‘gloss-1.13.2.1’.
Perhaps you need to add ‘gloss’ to the build-depends in your .cabal file.
Use -v (or `:set -v` in ghci) to see a list of the files searched for.
|
4 | import Graphics.Gloss
| ^^^^^^^^^^^^^^^^^^^^^
I am unsure what the problem here is and how to solve it.
You have a separate library stanza in your package.yaml. You need to add the gloss dependency there.
Related
I have a several executable targets in the project, like:
...
app/
other_app/
src/
package.yaml
stack.yaml
...
so, I have obviously different .hs files in app/, other_app/, src/. If I build it with stack tool then it build apps and other_apps executables from their dependencies, ie, if some .hs file changed in src/ - the result executable will be rebuild. Otherwise - no. stack knows a graph of dependencies like GNU make does it. How to list/print this graph? For example, for C I have makedepend tool which is able to extract dependencies recursively from .c files. Is it possible to be done for Haskell files? With stack tool itself? Maybe with a cabal tool? I tried, for example, v2-freeze of the cabal tool, but it is not related to the problem.
UPDATE:
package.yaml looks like:
.............
executables:
app1-exe:
main: Main.hs
source-dirs: app1
ghc-options:
- -threaded
- -rtsopts
- -with-rtsopts=-N
dependencies:
- app1
app2-exe:
main: Main.hs
source-dirs: app2
ghc-options:
- -threaded
- -rtsopts
- -with-rtsopts=-N
dependencies:
- app1
............
and now I want to list recursively dependencies (in Makefile-style, not dependencies on packages, like stack dot does it!), for instance for app2's Main.hs, something like:
src/Component1/Types.hs
src/Component1/Utils.hs
src/CoolLibrary/CoolUtility.hs
...
I am new to Haskell. I want to use Control.Lens package. I've read this and applied what it says but I get an error that says:
Resolving dependencies...
cabal-3.6.2.0.exe: Cannot build the executables in the package lens because it
does not contain any executables. Check the .cabal file for the package and
make sure that it properly declares the components that you expect.
when I try to run cabal install lens in the project folder.(I opened terminal in the project folder.)
Any help would be appreciated.
Solution: I've learned that I need to add 'lens' into build-depends part of .cabal file.Then I need to import Control.Lens inside Main.hs . I give my .cabal file as an example:
executable Prelude3
main-is: Main.hs
-- Modules included in this executable, other than Main.
--other-modules: Basic
-- LANGUAGE extensions used by modules in this package.
-- other-extensions:
build-depends: containers,lens,microlens,microlens-platform,base ^>=4.14.3.0
hs-source-dirs: app
default-language: Haskell2010
On the top of the Main.hs I write import Control.Lens. Finally after I run 'cabal build' and cabal run in the terminal necessary packages successfully downlaoaded.
First off, I'm new to using cabal and external packages with Haskell.
I'm trying to use the Graphics.Gloss package inside of MyLib. I can make it work if I include gloss in both the build-depends of library and executable.
Here is the relevant portion of the cabal file:
library
exposed-modules: MyLib
build-depends: base ^>=4.13.0.0,
gloss ^>=1.13.1.1
default-language: Haskell2010
executable ray-tracer
main-is: Main.hs
other-modules: MyLib
build-depends: base ^>=4.13.0.0, ray-tracer,
haskell-say ^>=1.0.0.0,
gloss ^>=1.13.1.1
MyLib.hs
module MyLib (someFunc) where
import Graphics.Gloss
someFunc :: IO ()
someFunc = display (InWindow "My Window" (200,200) (10,10)) white (Circle 80)
Main.hs
module Main where
import qualified MyLib (someFunc)
import HaskellSay (haskellSay)
main :: IO ()
main = do
MyLib.someFunc
Why doesn't this work when gloss is only included in the library dependencies?
You can make it work. There is a problem in your current set up, which is that the files for the library and the executable are in the same directory. See also this question How to avoid recompiling in this cabal file? which is a symptom of the same underlying problem: when you build the executable, it rebuilds MyLib from scratch (which requires the gloss dependency) instead of reusing your library that was already built.
MyLib/
ray-tracer.cabal
MyLib.hs
Main.hs # Bad
Move the .hs files in separate directories (technically you only need to move one of them, but I think it's better to keep the root directory as uniform as possible):
MyLib/
MyLib.cabal
src/
MyLib.hs
exe/
Main.hs
And in the cabal file, add hs-source-dirs: src and hs-source-dirs: exe to the corresponding sections:
library
hs-source-dirs: src
...
executable ray-tracer
hs-source-dirs: exe
...
I'm currently not using stack at all on this project (just Cabal), and all was going well when everything was in Main.hs. I decided to split up code, moving my dhall dep and related code from my executable deps to my library deps, and now seem to have this strange error when running cabal new-build:
Building executable 'FarmDataServer.exe' for FarmDataServer-0.1.0.0..
<no location info>: warning: [-Wmissing-home-modules]
These modules are needed for compilation but not listed in your .cabal file's other-modules: FDS
FDS.Config.Core
FDS.Config.DhallConf
[2 of 4] Compiling FDS.Config.DhallConf ( src/FDS/Config/DhallConf.hs, /home/brandon/workspace/CIDA/FarmDataServer/dist-newstyle/buil
d/x86_64-linux/ghc-8.4.4/FarmDataServer-0.1.0.0/x/FarmDataServer.exe/build/FarmDataServer.exe/FarmDataServer.exe-tmp/FDS/Config/Dhall
Conf.o )
src/FDS/Config/DhallConf.hs:7:1: error:
Could not find module `Dhall'
Use -v to see a list of the files searched for.
|
7 | import Dhall
| ^^^^^^^^^^^^^^^^^^^^^^
Certainly I'm also a bit confused by the Wmissing-home-modules message since I seem to have added those in my cabal file.
Relevant bits of my .cabal file:
cabal-version: 2.4
name: FarmDataServer
version: 0.1.0.0
library
exposed-modules:
FDS
other-modules:
FDS.Config.Core
, FDS.Config.DhallConf
build-depends: base ^>=4.11.1.0
, conduit ^>=1.3.1
, csv-conduit ^>=0.7.0.0
, dhall ^>=1.20.0
, text ^>=1.2.3.1
hs-source-dirs: src
executable FarmDataServer.exe
main-is: Main.hs
build-depends: base ^>=4.11.1.0
, conduit ^>=1.3.1
, csv-conduit ^>=0.7.0.0
, scotty ^>=0.11.3
, text ^>=1.2.3.1
, FarmDataServer ^>=0.1.0.0
My src folder:
$ pwd
/home/brandon/workspace/CIDA/FarmDataServer/src
$ du -a
4 ./FDS/Config/DhallConf.hs
4 ./FDS/Config/Core.hs
12 ./FDS/Config
16 ./FDS
4 ./FDS.hs
4 ./Main.hs
28 .
For the missing modules, sink your program executable into a directory such that the module hierarchy for yoru library isn't visible:
mkdir program ; mv src/Main.hs program/
and in cabal for the executable
hs-source-dirs: program
For your missing module Dhall, add the dhall build dependency to your executable stanza in the cabal file.
Within my project's .cabal file I've got the following under the executable section:
executable ArchPkgstatsScraper
hs-source-dirs: app
main-is: Main.hs
ghc-options: -threaded -rtsopts -with-rtsopts=-N
build-depends: base
, ArchPkgStatsScraper
, text
, conduit
, html-conduit
, http-conduit
, xml-conduit
, resourcet
, transformers
After I've successfully installed / built the above with stack, how could I check which version of xml-conduit is installed?
The command
stack ls dependencies
or for older version of stack:
stack list-dependencies
will list every dependency installed for the current project, along with its version.
The new command is going to be
stack ls dependencies
which is replacement of stack list-dependencies
You can read more about it here