Could not load module 'System.Random'

Question

I could not add System.Random module to use it my source haskell file.

import System.Random

This is the error produced by stack ghc:

/Users/admin1/Haskell/PROJECTS/L4/src/Lib4.hs:32:1: error:
Could not load module ‘System.Random’
It is a member of the hidden package ‘random-1.1’.
You can run ‘:set -package random’ to expose it.
(Note: this unloads all the modules in the current scope.)
Use -v (or `:set -v` in ghci) to see a list of the files searched for.
   |
32 | import System.Random
   | ^^^^^^^^^^^^^^^^^^^^
Failed, five modules loaded.

Thank you very much in advance. P.S. I am using Stack and GHC versions: Version 2.3.1, Git revision x86_64 hpack-0.33.0, ghc-8.8.3 on Mac OSX

user_67579 · Answer

As the error says:

It is a member of the hidden package ‘random-1.1’.

This likely means that you did not list it in the build-depends, and thus it is not exposed to your modules.

You can alter the .cabal file, and add it, for example:

-- project.cabal file
-- …

executable …
  -- …
  build-depends:
      base >= 4.7 && < 5
    , random >= 1.1
    -- ,  …

Could not load module 'System.Random'

1 Answers