[Haskell-beginners] State Monad

[Mike Meyer]

On Fri, Apr 17, 2015 at 2:25 PM, Thomas Jakway <tjakway at nyu.edu> wrote:

> genThree listMax = do --highest index in the list
>         let listMin = 0 :: Int --lowest index in the list
>         generatedMin <- state randomR (listMin, listMax)
>         return generatedMin
>

What you're missing is a $:

The only chagne to our genThree functions is making it "state $" instead of
"state".


#!/usr/bin/env runhaskell

import System.Random
import Control.Monad.State

genThree listMax = do --highest index in the list
        let listMin = 0 :: Int --lowest index in the list
        generatedMin <- state $ randomR (listMin, listMax)
        return generatedMin

main = do
  gen <- newStdGen
  print $ evalState (genThree 10) gen
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