definition module Sokoban

from StdString import class toString

:: SokobanPuzzle = Sokoban [[SokobanTile]]
:: SokobanTile = Free | Wall | Box | Target | Agent | TargetAgent | TargetBox

instance toString SokobanTile
instance toString SokobanPuzzle

parse :: String *World -> (SokobanPuzzle, *World)
parseFromFile :: *File -> (SokobanPuzzle, *File)

numberOfBlocks :: SokobanPuzzle -> Int