[Haskell-beginners] netwire accum delayed by one

[Nathan Hüsken]

Hey,

With this netwire based program:

{-# LANGUAGE Arrows #-}
import Control.Wire
import Data.List

mainWire :: WireP () Double
mainWire = proc _ -> do
  accum (+) 0 -< 1

main = do
  wireLoop mainWire

wireLoop :: WireP () Double -> IO ()
wireLoop w' = do
    let (mx, w) = stepWireP w' 1.0 ()
    case mx of
      Left x  -> putStrLn $ show mx
      Right x -> putStrLn $ show mx
    wireLoop w

I get (output):

Right 0.0
Right 1.0
Right 2.0
...

Should the output not start with 1.0 (and not 0.0)? The accum should be
applied already in the first invocation, should it not?

Regards,
Nathan