Wsrtjtyk

In app/Main.hs, I want to open a text file, "foo.txt". I know how to open a text file in a plain Haskell program. In my cabal project,

import System.IO



Main = do

    contents <- readFile "foo.txt"

    print $ Main.lex contents

    return contents





type Keyword = String

lex :: String -> [Keyword]

lex "" = 

lex x = words x

gives the error

openFile: does not exist (No such file or directory)

What do I need to change in my cabal file, or the file path or location to be able to open the file? I've tried putting it next to the output binary, and that doesn't work either.

This is my cabal file:

-- This file has been generated from package.yaml by hpack version 0.28.2.

--

-- see: https://github.com/sol/hpack

--

-- hash: baf2fc7e230f4b4937dfd918a13fefb55b66c7a4468b24d0e3e90cad675b26d5



name:           CCompiler

version:        0.1.0.0

description:    Please see the README on GitHub at <https://github.com/githubuser/CCompiler#readme>

homepage:       https://github.com/githubuser/CCompiler#readme

bug-reports:    https://github.com/githubuser/CCompiler/issues

author:         Author name here

maintainer:     example@example.com

copyright:      2018 Author name here

license:        BSD3

license-file:   LICENSE

build-type:     Simple

cabal-version:  >= 1.10

extra-source-files:

    ChangeLog.md

    README.md



source-repository head

  type: git

  location: https://github.com/githubuser/CCompiler



library

  exposed-modules:

      Lib

  other-modules:

      Paths_CCompiler

  hs-source-dirs:

      src

  build-depends:

      base >=4.7 && <5

  default-language: Haskell2010



executable CCompiler-exe

  main-is: Main.hs

  other-modules:

      Paths_CCompiler

  hs-source-dirs:

      app

  ghc-options: -threaded -rtsopts -with-rtsopts=-N

  build-depends:

      CCompiler

    , base >=4.7 && <5

  default-language: Haskell2010



test-suite CCompiler-test

  type: exitcode-stdio-1.0

  main-is: Spec.hs

  other-modules:

      Paths_CCompiler

  hs-source-dirs:

      test

  ghc-options: -threaded -rtsopts -with-rtsopts=-N

  build-depends:

      CCompiler

    , base >=4.7 && <5

  default-language: Haskell2010

add

data-dir: data

in the top section of the cabal file.

create the directory 'data' next to src and app, and put all files in there.

Make sure your cabal file also has this line

other-modules:

  Paths_CCompiler

with your project's name instead of CCompiler.

My main function is now this

module Main where



import Lib

import System.IO

import Paths_CCompiler



main = do

    filepath <- getDataFileName "return_2.c"

    contents <- readFile filepath

    print $ Lib.lex contents

    return contents

Thanks to this blog post.

I understand your question to be about finding files at runtime, which you want to process and aren't packaged with your package.

Where are severals ways, how you could find files at runtime, which aren't packaged.

Either add an command line flag and call your executable with the absolute path of the file you want to process.

Or implement a file chooser dialog, with e.g. gi-gtk.

Or hard coding relative paths which isn't advisable, as they are interpreted relative to the current working directory of your process, which can be different, depending on how the program did get started.

If you want to determine, which current working directory your program runs in, if started with cabal run, just do a litte test project with the following cabal file:

name: test2

build-type: Simple

cabal-version: >= 1.10

version: 0.0.0.1



executable test2

  hs-source-dirs: .

  main-is: test2.hs

  build-depends:

      base

    , directory

and the following test2.hs:

module Main where



import System.Directory



main :: IO ()

main = do

  cwd <- getCurrentDirectory

  putStrLn cwd