~/koodi/tmp >>> git clone https://github.com/moocfi/haskell-mooc                                                    
Cloning into 'haskell-mooc'...
remote: Enumerating objects: 615, done.
remote: Total 615 (delta 0), reused 0 (delta 0), pack-reused 615
Receiving objects: 100% (615/615), 619.20 KiB | 674.00 KiB/s, done.
Resolving deltas: 100% (398/398), done.
~/koodi/tmp >>> cd haskell-mooc/exercises                                                                           
~/.../haskell-mooc/exercises >>> stack build                                                               ±[master]
tests> configure (lib)
Configuring tests-0.0.1...
tests> build (lib)
Preprocessing library for tests-0.0.1..
Building library for tests-0.0.1..
tests> copy/register
Installing library in /home/sose/koodi/tmp/haskell-mooc/exercises/.stack-work/install/x86_64-linux-tinfo6/9f7a1b10dea2e1be7b9441ab5af84ef2074022c0ed98129fb7b5a429376b062f/8.6.5/lib/x86_64-linux-ghc-8.6.5/tests-0.0.1-AwNA4KT7DDkgDZZ9hF4zt
Registering library for tests-0.0.1..
~/.../haskell-mooc/exercises >>> stack ghci                                                                ±[master]
Configuring GHCi with the following packages: tests
GHCi, version 8.6.5: http://www.haskell.org/ghc/  :? for help
Loaded GHCi configuration from /tmp/haskell-stack-ghci/2a3bbd58/ghci-script
Prelude> :l Set4a
[1 of 2] Compiling Mooc.Todo        ( /home/sose/koodi/tmp/haskell-mooc/exercises/Mooc/Todo.hs, interpreted )
[2 of 2] Compiling Set4a            ( Set4a.hs, interpreted )

Set4a.hs:22:1: error:
    Could not load module ‘Data.Map’
    It is a member of the hidden package ‘containers-0.6.0.1’.
    You can run ‘:set -package containers’ to expose it.
    (Note: this unloads all the modules in the current scope.)
    Use -v to see a list of the files searched for.
   |
22 | import qualified Data.Map as Map
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Set4a.hs:23:1: error:
    Could not load module ‘Data.Array’
    It is a member of the hidden package ‘array-0.5.3.0’.
    You can run ‘:set -package array’ to expose it.
    (Note: this unloads all the modules in the current scope.)
    Use -v to see a list of the files searched for.
   |
23 | import Data.Array
   | ^^^^^^^^^^^^^^^^^
Failed, one module loaded.
*Mooc.Todo> :set -package containers
package flags have changed, resetting and loading new packages...
Prelude> :set -package array
package flags have changed, resetting and loading new packages...
Prelude> :l Set4a
[1 of 2] Compiling Mooc.Todo        ( /home/sose/koodi/tmp/haskell-mooc/exercises/Mooc/Todo.hs, interpreted )
[2 of 2] Compiling Set4a            ( Set4a.hs, interpreted )
Ok, two modules loaded.
*Set4a>