This repo provides a library for writing console-based programs in Elm.

Before you begin, compile and pull in the jsdom dependency. node.js by default installs dependencies locally so you should do this for each elm project you have using IO.

$ npm install jsdom

(On Windows, jsdom is somewhat difficult to install. Refer to this blog post for detailed instructions)

An elm Program:

module Main where

import IO.IO (..)
import IO.Runner (Request, Response, run)

import List
import Maybe
import String

echo : IO ()
echo = forever (getLine >>= putStrLn)

loop : IO ()
loop = getLine >>= \s ->
       if s == "exit"
       then pure ()
       else putStrLn s >>> loop
       
hello : IO ()
hello = putStrLn "Hello, Console!" >>>
        putStrLn "I'll echo your input until you say \"exit\":" >>>
        loop >>>
        putStrLn "That's all, folks! Here's some blahs:"  >>>
        putStrLn (String.concat <| List.repeat 100000 "blah ") >>>
        exit 0

port requests : Signal Request
port requests = run responses hello

port responses : Signal Response

link in some javascript and then run:

$ elm-make --yes Test.elm raw-test.js
...
$ ./elm-io.sh raw-test.js test.js
$ node test.js
Hello, Console!
I'll echo your input:
hooray
hooray
That's all, folks!

The basic interface is elm-io infile outfile, where infile is a compiled Elm file with requests and response signals set up as above and outfile is the desired filename for the compiled output.

If you have a problem first make sure:

1. You have jsdom installed

The implementation is based on the IOSpec haskell library.