I have tried to load a file by typing ghc Interact Interact.hs
This produces the following error:
<no location info>: error:
module ‘main:Main’ is defined in multiple files: Interact.hs
Interact.hs``
I therefore searched on stack overflow and found the answers here (stack ghci with error module ‘main:Main’ is defined in multiple files:) which seem relevant.
However, unfortunately, they are undecipherable for the uninitiate, taking for granted concepts that I do not have at my disposal. For example, what are the following two sentences even suggesting?
I would run Stack with --verbose and see how GHCi is being invoked, and double-check the package.yaml and generated Cabal file. (If you edit your question to include that, we may be able to offer more specific help with it.)
I don't know what it means to check a package or a generated Cabal file (nor what a generated cabal file in). There is not definition of what is meant by 'invoked'.
I'm sure that the answers in the link above are very useful to those who already possess the requisite concepts. But to the uninitiated, they don't help.
Can someone please provide answers which clarify the particular questions I have above, so that I can understand the information provided in stack ghci with error module ‘main:Main’ is defined in multiple files:?
I typed stack --verbose into the terminal and this produced
Missing: COMMAND|FILE
Usage: stack [--help] [--version] [--numeric-version] [--hpack- numeric-version]
[--docker*] [--nix*] ([--verbosity VERBOSITY] | [-v|--verbose] |
[--silent]) [--[no-]time-in-log] [--stack-root STACK-ROOT]
[--work-dir WORK-DIR] [--[no-]system-ghc] [--[no-]install-ghc]
[--arch ARCH] [--ghc-variant VARIANT] [--ghc-build BUILD]
[-j|--jobs JOBS] [--extra-include-dirs DIR] [--extra-lib-dirs DIR]
[--with-gcc PATH-TO-GCC] [--with-hpack HPACK]
[--[no-]skip-ghc-check] [--[no-]skip-msys] [--local-bin-path DIR]
[--[no-]modify-code-page] [--[no-]allow-different-user]
[--[no-]dump-logs] [--resolver RESOLVER] [--compiler COMPILER]
[--[no-]terminal] [--color WHEN] [--terminal-width INT]
[--stack-yaml STACK-YAML] COMMAND|FILE
You gave GHC the same file twice. GHC will automatically try finding a file by adding appropriate file extensions, so when you gave it Interact it found Interact.hs once, then you gave it the same file again.
I'm not sure what you were trying to achieve with your command. If you are trying to add a directory called Interact that GHC will search for modules, you want ghc -iInteract Interact.hs. If you are trying to name the binary that GHC outputs, you want ghc -o Interact Interact.hs (but that would be the default name anyway, so in that case you might as well just use ghc Interact.hs).
The stack documentation is probably irrelevant to you since you are using ghc directly.
Related
I'm learning Haskell for the first time and I can't see to understand why the ghci can't find the file I'm trying to compile. Especially since, I saved the file. This is my file,
import System.IO
trueAndFalse = True && False
Now this is what I ran in the compiler,
<no location info>: error: can't find file: tut-1.hs
Failed, no modules loaded.
The "Failed, no modules loaded." makes me think you're talking about ghci. If so, you can find out where ghci is looking for files with :show paths. Here's what it looks like when I try:
> :show paths
current working directory:
/home/<my username>
module import search paths:
.
The module import search paths tells you what directories it's looking in. A lone . in that list refers to the current working directory. So, for me, if I wanted a file to be easily accessible from that ghci instance, I would have to save it in /home/<my username>.
Of course there are ways of changing all of these pieces -- which paths are in the import search path, which directory is the current working directory, and so forth -- but this should get you going for simple usage.
And, by the way, a note on terminology: the GHC tool suite comes with both a compiler and an interpreter. The compiler's executable is ghc, and the interpreter's executable is ghci. Knowing about that distinction may help you avoid confusion in future conversations!
I've been able to use the Data.Tuple.Extra module after installing the extra package by stack build extra. But the same doesn't apply to the Data.List.Unique module (https://hackage.haskell.org/package/Unique-0.4.7.8/docs/Data-List-Unique.html). According to the website, it's included in package Unique. So, I installed it with
$ stack build Unique
The installation seems to have been successful because I didn't see any error messages. But
$ cat try.hs
import Data.List.Unique
main = do putStrLn "hello"
$ stack runghc try.hs
try.hs:1:1: error:
Could not find module ‘Data.List.Unique’
Use -v (or `:set -v` in ghci) to see a list of the files searched for.
|
1 | import Data.List.Unique
| ^^^^^^^^^^^^^^^^^^^^^^^
$
The output from stack runghc -v try.hs is too big for me to analyze . . .
Note: I've modified the question to focus on the installation and use of modules. Following the answers provided below, I'm able to run the program using an option. Still, it would be nice if one wouldn't need to use a package option.
stack build doesn't "install" the package globally for use with every compilation, and runghc can't pick up Stack packages. It's meant to be a more or less direct execution of GHC.
You can specify packages to use if you run your program with stack try.hs, as described in the docs. In that case, you'll be able to specify packages to use with specially formatted comments, like this:
-- stack script --package Unique
import Data.List.Unique
main = do putStrLn "hello"
The Unique dependency can be specified by passing the --package option to runghc:
stack runghc --package Unique try.hs
Alternatively, you can make try.hs a Stack script, as illustrated by Fyodor Soikin's answer.
If you plan to develop try.hs into more than a standalone file, consider setting up a Stack project. See the Hello World example in the Stack User Guide for initial guidance on that.
A minimal reproduction can be found here:
https://github.com/IvanMalison/stack-gtk2hs-bug
Everything works as expected when I use normal stack commands, but when I run the failing command:
stack ghc -- --make main.hs
I get the following error:
main.hs:3:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
main.hs:4:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk.Abstract.Widget’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
main.hs:5:1: error:
Ambiguous interface for ‘Graphics.UI.Gtk.Layout.Table’:
it was found in multiple packages: gtk-0.14.6 gtk3-0.14.6
The output of stack exec ghc-pkg -- --no-user-package-db list is https://gist.github.com/f19f900988f49e4d03cd61f1cab48baa . This output makes me expect that the reason that this is happening is that some other stack install required gtk (not gtk3 which is what is specified as a dependency in this package) and somehow this package is visible from the stack ghc command for some reason.
Am I misunderstanding the stack ghc command? Shouldn't this essentially do the same thing as stack build?
There's no builtin way to do this with stack currently. However, it is possible to get stack ghci to do this. The most straightforward way to do it is to make a cabal package which has the executable target. However, if you really want to just use straight ghc, there is a way. Copy-pasting from my comment here:
stack ghc works a bit differently than stack ghci. It's essentially a synonym for stack exec -- ghc, which will run the right compiler with the right databases, but won't set up anything related to your local packages like include directories etc. Note that stack ghci takes TARGET arguments whereas stack ghc does not. Retrospectively, this is a bit inconsistent, but stack ghc came before stack ghci.
It does make sense to have the ability to do something like this, though not sure how to best achieve that. Some potential options:
--no-interactive argument on stack ghci. Would be a bit obtuse. Weird to run a ghci command when, though it would be using the stack ghci logic.
Add --target TARGET option to stack ghc, to tell it to use the environment of a particular local package target.
Here's a workaround for now. Put the following in ~/.local/bin/stack-run-ghc.sh and make it user executable:
#/bin/sh
ghc $(echo "$*" | sed 's/--interactive//g')
This takes the arguments, removes --interactive, and calls ghc. With this, I can build stack using ghc via the following:
stack ghci --with-ghc stack-run-ghc.sh --ghci-options src/main/Main.hs
I am attempting to set up a new Stack project on NixOS with GHCJS as the compiler following the instructions at http://docs.haskellstack.org/en/stable/ghcjs.html
I have included in my stack.yaml file the following lines of code (all on one line because tab spaces seem to give issues):
# Compiler specifying the GHCJS compiler for this project (using improved base).
compiler: ghcjs-0.2.0.20151230.3_ghc-7.10.2
compiler-check: match-exact
setup-info:
ghcjs: source:
ghcjs-0.2.0.20151230.3_ghc7.10.2:
url: "https://github.com/nrolland/ghcjs/releases/download/v.0.2.0.20151230.3/ghcjs-0.2.0.20151230.3.tar.gz"
and I have retrieved the following error message when I ran stack setup
Could not parse '/home/lorkaan/pandocJS/stack.yaml':
InvalidYaml (Just (YamlParseException {yamlProblem = "mapping values are not allowed in this context", yamlContext = "", yamlProblemMark = YamlMark {yamlIndex = 487, yamlLine = 12, yamlColumn = 17}}))
See https://github.com/commercialhaskell/stack/blob/release/doc/yaml_configuration.md.
Additionally, I tried removing the setup-info field because Stack was complaining about it, leaving my stack.yaml file like:
# Compiler specifying the GHCJS compiler for this project (using improved base).
compiler: ghcjs-0.2.0.20151230.3_ghc-7.10.2
compiler-check: match-exact
which produces this output with the stack setup command:
Warning: /home/lorkaan/pandocJS/stack.yaml: Unrecognized field in ProjectAndConfigMonoid: compiler
Preparing to install GHC to an isolated location.
This will not interfere with any system-level installation.
Already downloaded.
The following executables are missing and must be installed: make
Does anybody have any idea why this would be happening?
the first error is because of a basic syntax error in your YAML configuration. The correct version would be:
setup-info:
ghcjs:
source:
ghcjs-0.2.0.20151230.3_ghc7.10.2:
url: "https://github.com/nrolland/ghcjs/releases/download/v.0.2.0.20151230.3/ghcjs-0.2.0.20151230.3.tar.gz"
The second error is because of exactly what it says: you are lacking the make utility. You need to use your Linux distribution's package management system to install make. Since I don't know which distribution you are on, I can only recommend simply executing the $ make command and seeing if the environment is smart enough to point out which package it can be found in. Ubuntu typically does that. Then it's only a matter of apt-get install-ing the package, or possibly yum install-ing on e.g. CentOS and Fedora, etc.
P.S. questions like yours normally get a downvote for not having shown sufficient effort in diagnosing the problem (or for putting 2 totally separate problems under a single question) but I'm giving you the benefit of the doubt and just hoping you'll be tidier next time.
I have annotated my code in Haddock style and would like to generate browse-able documentation. Since I am also using stack, I want to integrate the documentation generation into the workflow. However, I have not yet been able to generate anything useful.
I can run
stack haddock
and it will generate documentation in the style I want (to be found deep inside ~/.stack/), but it only seems to generate documentation for the packages I depend on, rather than for my own code.
When I run
stack haddock --help
I get the impression that I can use the additional argument --haddock to generate documentation for my own project, and --no-haddock-deps to leave out the documentation for my dependencies. However, when I run
stack haddock --haddock --no-haddock-deps
nothing seems to happen. If I stack clean first it will recompile all my code but no output is generated seeming to relate in any way to documentation.
As an intermediate solution I have also tried running Haddock by itself, i.e.
haddock my-source.hs
but then I get an error that it cannot find a module the file depends on (which is installed locally by stack). This gives me the impression that documentation generation will have to go through stack somehow. I have looked for, but not really found any explanations related to configuring my .cabal and stack.yaml files for documentation.
TL;DR
How can I use stack and Haddock to generate documentation for the code in my own package?
According to this ticket on the stack issue tracker, Stack can currently only build documentation for libraries, but not executables.
Cabal can be configured to work with the stack databases with this command:
cabal configure --package-db=clear --package-db=global --package-db=$(stack path --snapshot-pkg-db) --package-db=$(stack path --local-pkg-db)
after which you can run cabal haddock --executables to generate the documentation.
By the way, stack haddock is only a shortcut for stack build --haddock, so there is no need to write stack haddock --haddock.
https://www.reddit.com/r/haskell/comments/5ugm9s/how_to_generate_haddock_docs_for_nonlibrary_code/ddtwqzc/
The following solution only works when individual files are specified:
stack exec -- haddock --html src/Example.hs src/Main.hs --hyperlinked-source --odir=dist/docs