Debug.hs

-- |
-- Copyright  : (c) Ivan Perez, 2017-2022
-- License    : BSD-style (see the LICENSE file in the distribution)
-- Maintainer : ivan.perez@keera.co.uk
--
-- Debug FRP networks by inspecting their behaviour inside.
module FRP.Yampa.Debug where

-- External imports
import Debug.Trace      (trace)
import FRP.Yampa        (SF, arr)
import System.IO.Unsafe (unsafePerformIO)

-- | Signal Function that prints the value passing through using 'trace'.
traceSF :: Show a => SF a a
traceSF = traceSFWith show

-- | Signal Function that prints the value passing through using 'trace', and a
-- customizable 'show' function.
traceSFWith :: (a -> String) -> SF a a
traceSFWith f = arr (\x -> trace (f x) x)

-- | Execute an IO action using 'unsafePerformIO' at every step, and ignore the
-- result.
traceSFWithIO :: (a -> IO b) -> SF a a
traceSFWithIO f = arr (\x -> unsafePerformIO (f x >> return x))