[Haskell-cafe] state monad transformer that adds or combines state
dennis.raddle at gmail.com
Tue May 15 05:27:19 UTC 2018
I find myself using the state and exception monads at large scale in my
programs. For instance I often keep a pseudorandom generator as the state,
and use exception handling.
In local computations, I may want to use some additional state. Is there a
way to add a little extra state temporarily?
Let's say I have
data State1 = State1 StdGen
type M1 = State State1
data State2 = State2 State1 Int
type M2 = State State2
runM2 :: M2 a -> Int -> M1 a
someFunc :: M1 Double
someFunc = do
r <- <compute something pseudorandomly>
r2 <- runM2 (deeperFunc r) 3
deeperFunc :: Double -> M2 Double
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