[Haskell-cafe] State Monad

[Mark Carroll]

On Fri, 4 Mar 2005, Mark Carroll wrote:
(snip)
> Enclosed is a programme that asks for two ints from standard input, adds
(snip)

Let me try again. (-:

-- Mark
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module StackMTest
where
import StackM
import Control.Monad
import Control.Monad.Trans
import System.IO
import System.Random

add :: Num a => StackM a IO ()

add =
    do x <- popM
       y <- popM
       pushM (x + y)

throwTenDie :: StackM Int IO ()

throwTenDie = lift (getStdRandom (randomR (1, 10))) >>= pushM

stackMTest :: StackM Int IO Int

stackMTest =
    do pushNumber
       pushNumber
       throwTenDie
       add
       add
       popM
    where
    pushNumber =
        do text <- lift $ getLine
           pushM (read text)

main :: IO ()

main = runStackM stackMTest >>= print