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.
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