purescript passing impure callbacks

Main.purs

module Main where

import Prelude

import Data.Foreign.EasyFFI

import Control.Monad.Eff (Eff)
import Control.Monad.Eff.Console (CONSOLE, log)

-- code for wrapping impure functions

newtype Impure f = Impure f

mkImpureFn1 :: ∀ a e v. (a -> Eff e v) -> Impure (a -> v)
mkImpureFn1 f = Impure (unsafeForeignFunction ["f", "a"] "f(a)();" f)

-- original Eff function

test1 :: ∀ e. String -> Eff (console :: CONSOLE | e) Unit
test1 x = log ("test: " <> x)

-- impure version of test1

test2 :: Impure (String -> Unit)
test2 = mkImpureFn1 test1

-- external function expecting impure callback

testFunction = unsafeForeignProcedure ["cb",""] "console.log(\"expecting impure function\"); cb(\"a\");"

-- test Eff version and Impure version

main :: forall e. Eff (console :: CONSOLE | e) Unit
main = do
  let f1 = test1
  let f2 = test2
  log "test1 --"
  _ <- testFunction f1
  log "--"
  log "test2 --"
  _ <- testFunction f2
  log "--"
  pure unit

output.txt

Compiling Main
PSCi, version 0.11.6
Type :? for help

import Prelude
> import Main
> main
test1 --
expecting impure function
--
test2 --
expecting impure function
test: a
--
unit

>