Trying to install System.Random on stack

Question

I'm using stack 1.6.1. In src/Main.hs I start with

module Main where

import System.IO
import System.Random
...

I do not use anything from System.Random at this time.

When I run stack ghci I get

/Users/mkaravan/end2end/Music/music/src/Main.hs:4:1: error:
    Could not find module ‘System.Random’
    Use -v to see a list of the files searched for.
  |
4 | import System.Random
  | ^^^^^^^^^^^^^^^^^^^^

I've had no luck with any of the following commands:

stack install System.Random
stack install system.random
stack install random

I get this error:

>>> stack install System.Random
Error parsing targets: Directory not found: System.Random

How do I get System.Random to run in Stack?

Answer 1

Probably the most straightforward command is stack ghci --package random . But in theory stack install random should have worked as well. However, since you haven't included the output from that call, it's not clear what didn't work with it.

Answer 2

You probably need to add random to the dependencies section in your package.yaml (or if you are not using hpack, to build-depends in *.cabal ). This tells stack that the package depends on the random package, which contains the System.Random module.