wtf.hs

module Kumochan where

import Monad
import Control.Monad.State

data Env = Env {nodeId::Int, symId::Int} deriving (Show)

root = Env (-1) (-1)

nextNodeId :: Env -> (Int, Env)
nextNodeId = runState (do (Env a b) <- get
                          a'        <- return $ a + 1
                          put $ Env a' b
                          return a')

-- no problem, replacing nextNodeId with:

nextSymId :: Env -> (Int, Env)
nextSymId = runState (do (Env a b) <- get
                          b'        <- return $ b + 1
                          put $ Env a b'
                          return b')

-- is also no problem, yet pasting the second after the first
-- results in: the last statement in a do construct must be an expression