Ertugrul Soeylemez writes:
I find myself writing the following very often:
system :: Wire IO () String system = proc _ -> do botAddPeriod <- succ ^<< noise -< () botAddSpeed <- noise1 -< () botAddStart <- noise1 -< () botMsg <- event addBot -< (botAddPeriod, botAddSpeed, botAddStart)
bots <- manager -< ((), maybe MgrNop id botMsg) let botStr = concatMap (printf "%8.2") . M.elems $ bots :: String identity -< printf "Bot positions: %s" botStr
where addBot :: Wire IO (Double, Double, Double) (MgrMsg Int IO () Double) addBot = proc (addPeriod, addSpeed, addStart) -> do periodically -< addPeriod botId <- identifier -< () identity -< MgrAdd botId (constant addSpeed >>> integral addStart)
If addPeriod is supposed to be the same as botAddPeriod, etc, this should be equivalent: system :: Wire IO () String system = proc _ -> do addPeriod <- succ ^<< noise -< () addSpeed <- noise1 -< () addStart <- noise1 -< () botMsg <- (|event (do periodically -< addPeriod botId <- identifier -< () identity -< MgrAdd botId (constant addSpeed >>> integral addStart))|) bots <- manager -< ((), maybe MgrNop id botMsg) let botStr = concatMap (printf "%8.2") . M.elems $ bots :: String identity -< printf "Bot positions: %s" botStr See the GHC Arrow notation documentation for more about the banana brackets, which let you use user-defined control structures like event.