creatures

    No instance for (Functor f0) arising from a use of ‘creatures’
    The type variable ‘f0’ is ambiguous
    Relevant bindings include
      player :: (Creature -> f0 Creature) -> GameState -> f0 GameState
        (bound at src/GameState.hs:75:1)
    Note: there are several potential instances:
      instance Functor (Const m) -- Defined in ‘Control.Applicative’
      instance Control.Arrow.Arrow a =>
               Functor (Control.Applicative.WrappedArrow a b)
        -- Defined in ‘Control.Applicative’
      instance Monad m => Functor (Control.Applicative.WrappedMonad m)
        -- Defined in ‘Control.Applicative’
      ...plus 42 others
    In the first argument of ‘(.)’, namely ‘creatures’
    In the expression: creatures . ix 0
    In an equation for ‘player’: player = creatures . ix 0

ix

    No instance for (Applicative f0) arising from a use of ‘ix’
    The type variable ‘f0’ is ambiguous
    Relevant bindings include
      player :: (Creature -> f0 Creature) -> GameState -> f0 GameState
        (bound at src/GameState.hs:75:1)
    Note: there are several potential instances:
      instance Monoid m => Applicative (Const m)
        -- Defined in ‘Control.Applicative’
      instance Control.Arrow.Arrow a =>
               Applicative (Control.Applicative.WrappedArrow a b)
        -- Defined in ‘Control.Applicative’
      instance Monad m =>
               Applicative (Control.Applicative.WrappedMonad m)
        -- Defined in ‘Control.Applicative’
      ...plus 29 others
    In the second argument of ‘(.)’, namely ‘ix 0’
    In the expression: creatures . ix 0
    In an equation for ‘player’: player = creatures . ix 0